Method and apparatus for channel state information reference signal (CSI-RS)

ABSTRACT

Methods and apparatuses for CSI reporting mechanisms are provided. A user equipment (UE) includes a transceiver and a processor operably connected to the transceiver. The transceiver is configured to receive information indicating a channel state information reference signal (CSI-RS) resource configuration, uplink-related downlink control information (DCI), and a CSI-RS associated with a selected CSI-RS resource in a same subframe as the uplink-related DCI. The processor configured to determine, in response to a CSI request included in the uplink-related DCI, an aperiodic CSI in reference to the CSI-RS. The transceiver is further configured to report the aperiodic CSI by transmitting the aperiodic CSI on an uplink channel.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.15/365,909, filed Nov. 30, 2016, which claims priority under 35 U.S.C. §119(e) to:

-   -   U.S. Provisional Patent Application Ser. No. 62/273,391 filed        Dec. 30, 2015;    -   U.S. Provisional Patent Application Ser. No. 62/319,653 filed        Apr. 7, 2016;    -   U.S. Provisional Patent Application Ser. No. 62/324,558 filed        Apr. 19, 2016;    -   U.S. Provisional Patent Application Ser. No. 62/340,148 filed        May 23, 2016;    -   U.S. Provisional Patent Application Ser. No. 62/356,799 filed        Jun. 30, 2016;    -   U.S. Provisional Patent Application Ser. No. 62/372,196 filed        Aug. 8, 2016;    -   U.S. Provisional Patent Application Ser. No. 62/378,272 filed        Aug. 23, 2016; and    -   U.S. Provisional Patent Application Ser. No. 62/406,443 filed        Oct. 11, 2016.        The above-identified provisional patent applications are hereby        incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to transmission method andchannel state information (CSI) reporting for multiple transmit antennaswhich includes two dimensional arrays. Such two dimensional arrays canbe associated with a type of multiple-input multiple-output (MIMO)system often termed “full-dimension” MIMO (FD-MIMO) or massive MIMO or3D-MIMO.

BACKGROUND

Wireless communication has been one of the most successful innovationsin modern history. The demand of wireless data traffic is rapidlyincreasing due to the growing popularity among consumers and businessesof smart phones and other mobile data devices, such as tablets, “notepad” computers, net books, eBook readers, and machine type of devices.To meet the high growth in mobile data traffic and support newapplications and deployments, improvements in radio interface efficiencyand coverage is of paramount importance.

A mobile device or user equipment can measure the quality of thedownlink channel and report this quality to a base station so that adetermination can be made regarding whether or not various parametersshould be adjusted during communication with the mobile device. Existingchannel quality reporting processes in wireless communications systemsdo not sufficiently accommodate reporting of channel state informationassociated with large, two dimensional array transmit antennas or, ingeneral, antenna array geometry which accommodates a large number ofantenna elements.

A transmission time interval for downlink (DL) channels is referred toas a subframe and can have, for example, duration of 1 millisecond.

SUMMARY

Various embodiments of the present disclosure provide methods andapparatuses for CSI reporting.

In one embodiment, a user equipment (UE) is provided. The UE includes atransceiver and a processor operably connected to the transceiver. Thetransceiver is configured to receive information indicating a channelstate information reference signal (CSI-RS) resource configuration,uplink-related downlink control information (DCI), and a CSI-RSassociated with a selected CSI-RS resource in a same subframe as theuplink-related DCI. The processor is configured to determine, inresponse to a CSI request included in the uplink-related DCI, anaperiodic CSI in reference to the CSI-RS. The transceiver is furtherconfigured to report the aperiodic CSI by transmitting the aperiodic CSIon an uplink channel.

In another embodiment, a base station (BS) is provided. The BS includesa processor and a transceiver operably connected to the processor. Theprocessor is configured to generate configuration information toconfigure a user equipment (UE) with channel state information referencesignal (CSI-RS) resource. The transceiver configured to transmit, to theUE, the CSI-RS resource configuration information, uplink-relateddownlink control information (DCI), and a CSI-RS associated with aselected CSI-RS resource in a same subframe as the uplink-related DCI.The transceiver is further configured to receive, from the UE, anaperiodic CSI reporting on an uplink channel. The aperiodic CSIreporting is determined in response to a CSI request included in theuplink-related DCI and in reference to the CSI-RS.

In another embodiment, a method for operating a UE is provided. Themethod includes receiving, by the UE, information indicating a channelstate information reference signal (CSI-RS) resource configuration, anuplink-related downlink control information (DCI), and a CSI-RSassociated with a selected CSI-RS resource in a same subframe as theuplink-related DCI; in response to receipt of a CSI request included inthe uplink-related DCI, determining, by the UE, an aperiodic CSI inreference to the CSI-RS; and reporting the aperiodic CSI by transmittingthe aperiodic CSI on an uplink channel.

The present disclosure relates to a pre-5th-Generation (5G) or 5Gcommunication system to be provided for supporting higher data ratesBeyond 4th-Generation (4G) communication system such as Long TermEvolution (LTE).

Other technical features may be readily apparent to one skilled in theart from the following figures, descriptions, and claims.

Before undertaking the DETAILED DESCRIPTION below, it can beadvantageous to set forth definitions of certain words and phrases usedthroughout this patent document. The term “couple” and its derivativesrefer to any direct or indirect communication between two or moreelements, whether or not those elements are in physical contact with oneanother. The terms “transmit,” “receive,” and “communicate,” as well asderivatives thereof, encompass both direct and indirect communication.The terms “include” and “comprise,” as well as derivatives thereof, meaninclusion without limitation. The term “or” is inclusive, meaningand/or. The phrase “associated with,” as well as derivatives thereof,means to include, be included within, interconnect with, contain, becontained within, connect to or with, couple to or with, be communicablewith, cooperate with, interleave, juxtapose, be proximate to, be boundto or with, have, have a property of, have a relationship to or with, orthe like. The term “controller” means any device, system or part thereofthat controls at least one operation. Such a controller can beimplemented in hardware or a combination of hardware and software and/orfirmware. The functionality associated with any particular controllercan be centralized or distributed, whether locally or remotely. Thephrase “at least one of,” when used with a list of items, means thatdifferent combinations of one or more of the listed items can be used,and only one item in the list can be needed. For example, “at least oneof: A, B, and C” includes any of the following combinations: A, B, C, Aand B, A and C, B and C, and A and B and C.

Moreover, various functions described below can be implemented orsupported by one or more computer programs, each of which is formed fromcomputer readable program code and embodied in a computer readablemedium. The terms “application” and “program” refer to one or morecomputer programs, software components, sets of instructions,procedures, functions, objects, classes, instances, related data, or aportion thereof adapted for implementation in a suitable computerreadable program code. The phrase “computer readable program code”includes any type of computer code, including source code, object code,and executable code. The phrase “computer readable medium” includes anytype of medium capable of being accessed by a computer, such as readonly memory (ROM), random access memory (RAM), a hard disk drive, acompact disc (CD), a digital video disc (DVD), or any other type ofmemory. A “non-transitory” computer readable medium excludes wired,wireless, optical, or other communication links that transporttransitory electrical or other signals. A non-transitory computerreadable medium includes media where data can be permanently stored andmedia where data can be stored and later overwritten, such as arewritable optical disc or an erasable memory device.

Definitions for other certain words and phrases are provided throughoutthis patent document. Those of ordinary skill in the art shouldunderstand that in many if not most instances, such definitions apply toprior as well as future uses of such defined words and phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsadvantages, reference is now made to the following description taken inconjunction with the accompanying drawings, in which like referencenumerals represent like parts:

FIG. 1 illustrates an example wireless network according to variousembodiments of the present disclosure;

FIGS. 2A and 2B illustrate example wireless transmit and receive pathsaccording to various embodiments of the present disclosure;

FIG. 3A illustrates an example user equipment according to variousembodiments of the present disclosure;

FIG. 3B illustrates an example enhanced NodeB (eNB) according to variousembodiments of the present disclosure;

FIG. 4 illustrates example two-dimensional (2D) antenna arraysconstructed from 16 dual-polarized elements arranged in a 4×2 or 2×4rectangular format which can be utilized in various embodiments of thepresent disclosure;

FIG. 5 illustrates an example procedure of operating aperiodic CSI-RS atan eNB and a UE according to various embodiments of the presentdisclosure;

FIG. 6 illustrates an example of CSI-RS resource reconfigurationmechanism for aperiodic CSI-RS according to various embodiments of thepresent disclosure;

FIG. 7A illustrates an example of MAC control element (MAC CE)transmission according to various embodiments of the present disclosure;

FIG. 7B illustrates an example format of MAC CE for CSI-RS resourceconfiguration pertaining to aperiodic CSI-RS according to variousembodiments of the present disclosure;

FIG. 8A illustrates an example of two-step aperiodic CSI-RS resourceconfiguration followed by resource selection according to variousembodiments of the present disclosure;

FIG. 8B illustrates an example format of MAC CE associated with thesecond step of aperiodic CSI-RS resource configuration according tovarious embodiments of the present disclosure;

FIG. 8C illustrates another example format of MAC CE associated with thesecond step of aperiodic CSI-RS resource configuration according tovarious embodiments of the present disclosure;

FIG. 8D illustrates another example format of MAC CE associated with thesecond step of aperiodic CSI-RS resource configuration according tovarious embodiments of the present disclosure;

FIG. 9 illustrates an example operation using activation/releasemechanism for the second step of aperiodic CSI-RS resource configurationaccording to various embodiments of the present disclosure;

FIG. 10 illustrates a flowchart for an example method wherein a UEreceives CSI-RS resource configuration information according to anembodiment of the present disclosure;

FIG. 11 illustrates a flowchart for an example method wherein a BSconfigures a UE with CSI-RS resource according to various embodiments ofthe present disclosure;

DETAILED DESCRIPTION

FIGS. 1 through 11, discussed below, and the various embodiments used todescribe the principles of the present disclosure in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the disclosure. Those skilled in the artwill understand that the principles of the present disclosure can beimplemented in any suitably arranged wireless communication system.

List of Acronyms

2D: two-dimensional MIMO: multiple-input multiple-output SU-MIMO:single-user MIMO MU-MIMO: multi-user MIMO 3GPP: 3rd generationpartnership project LTE: long-term evolution UE: user equipment eNB:evolved Node B or “eNB” BS: base station DL: downlink UL: uplink CRS:cell-specific reference signal(s) DMRS: demodulation reference signal(s)SRS: sounding reference signal(s) UE-RS: UE-specific reference signal(s)CSI-RS: channel state information reference signals SCID: scramblingidentity MCS: modulation and coding scheme RE: resource element CQI:channel quality information PMI: precoding matrix indicator RI: rankindicator MU-CQI: multi-user CQI CSI: channel state information CSI-IM:CSI interference measurement CoMP: coordinated multi-point DCI: downlinkcontrol information UCI: uplink control information PDSCH: physicaldownlink shared channel PDCCH: physical downlink control channel PUSCH:physical uplink shared channel PUCCH: physical uplink control channelPRB: physical resource block RRC: radio resource control AoA: angle ofarrival AoD: angle of departure

The following documents and standards descriptions are herebyincorporated by reference into the present disclosure as if fully setforth herein: 3GPP Technical Specification (TS) 36.211 version 12.4.0,“E-UTRA, Physical channels and modulation” (“REF 1”); 3GPP TS 36.212version 12.3.0, “E-UTRA, Multiplexing and Channel coding” (“REF 2”);3GPP TS 36.213 version 12.4.0, “E-UTRA, Physical Layer Procedures” (“REF3”); 3GPP TS 36.321 version 12.4.0, “E-UTRA, Medium Access Control (MAC)Protocol Specification” (“REF 4”); and 3GPP TS 36.331 version 12.4.0,“E-UTRA, Radio Resource Control (RRC) Protocol Specification” (“REF 5”).

To meet the demand for wireless data traffic having increased sincedeployment of 4G communication systems, efforts have been made todevelop an improved 5G or pre-5G communication system. Therefore, the 5Gor pre-5G communication system is also called a ‘Beyond 4G Network’ or a‘Post LTE System’.

The 5G communication system is considered to be implemented in higherfrequency (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higherdata rates. To decrease propagation loss of the radio waves and increasethe transmission distance, the beamforming, massive multiple-inputmultiple-output (MIMO), Full Dimensional MIMO (FD-MIMO), array antenna,an analog beam forming, large scale antenna techniques are discussed in5G communication systems.

In addition, in 5G communication systems, development for system networkimprovement is under way based on advanced small cells, cloud RadioAccess Networks (RANs), ultra-dense networks, device-to-device (D2D)communication, wireless backhaul, moving network, cooperativecommunication, Coordinated Multi-Points (CoMP), reception-endinterference cancellation and the like.

In the 5G system, Hybrid FSK and QAM Modulation (FQAM) and slidingwindow superposition coding (SWSC) as an advanced coding modulation(ACM), and filter bank multi carrier (FBMC), non-orthogonal multipleaccess (NOMA), and sparse code multiple access (SCMA) as an advancedaccess technology have been developed.

FIG. 1 illustrates an example wireless network 100 according to variousembodiments of the present disclosure. The embodiment of the wirelessnetwork 100 shown in FIG. 1 is for illustration only. Other embodimentsof the wireless network 100 could be used without departing from thescope of the present disclosure.

The wireless network 100 includes an eNodeB (eNB) 101, an eNB 102, andan eNB 103. The eNB 101 communicates with the eNB 102 and the eNB 103.The eNB 101 also communicates with at least one Internet Protocol (IP)network 130, such as the Internet, a proprietary IP network, or otherdata network. Instead of “eNB”, an alternative term “gNB” (general NodeB) can also be used. Depending on the network type, other well-knownterms can be used instead of “eNB” or “BS,” such as “base station” or“access point.” For the sake of convenience, the terms “eNB” and “BS”are used in this patent document to refer to network infrastructurecomponents that provide wireless access to remote terminals. Also,depending on the network type, other well-known terms can be usedinstead of “user equipment” or “UE,” such as “mobile station,”“subscriber station,” “remote terminal,” “wireless terminal,” or “userdevice.” For the sake of convenience, the terms “user equipment” and“UE” are used in this patent document to refer to remote wirelessequipment that wirelessly accesses an eNB, whether the UE is a mobiledevice (such as a mobile telephone or smartphone) or is normallyconsidered a stationary device (such as a desktop computer or vendingmachine).

The eNB 102 provides wireless broadband access to the network 130 for afirst plurality of user equipments (UEs) within a coverage area 120 ofthe eNB 102. The first plurality of UEs includes a UE 111, which can belocated in a small business (SB); a UE 112, which can be located in anenterprise (E); a UE 113, which can be located in a WiFi hotspot (HS); aUE 114, which can be located in a first residence (R); a UE 115, whichcan be located in a second residence (R); and a UE 116, which can be amobile device (M) like a cell phone, a wireless laptop, a wireless PDA,or the like. The eNB 103 provides wireless broadband access to thenetwork 130 for a second plurality of UEs within a coverage area 125 ofthe eNB 103. The second plurality of UEs includes the UE 115 and the UE116. In some embodiments, one or more of the eNBs 101-103 cancommunicate with each other and with the UEs 111-116 using 5G, LTE,LTE-A, WiMAX, or other advanced wireless communication techniques.

Dotted lines show the approximate extents of the coverage areas 120 and125, which are shown as approximately circular for the purposes ofillustration and explanation only. It should be clearly understood thatthe coverage areas associated with eNBs, such as the coverage areas 120and 125, can have other shapes, including irregular shapes, dependingupon the configuration of the eNBs and variations in the radioenvironment associated with natural and man-made obstructions.

As described in more detail below, one or more of eNB 101, eNB 102, andeNB 103 transmit to UEs 111-116 with precoder cycling and configure UEs111-116 for CSI reporting as described in embodiments of the presentdisclosure. In various embodiments, one or more of UEs 111-116 receiveand demodulate at least one transmission with precoder cycling as wellas perform calculation and reporting for of CSI.

Although FIG. 1 illustrates one example of a wireless network 100,various changes can be made to FIG. 1. For example, the wireless network100 could include any number of eNBs and any number of UEs in anysuitable arrangement. Also, the eNB 101 could communicate directly withany number of UEs and provide those UEs with wireless broadband accessto the network 130. Similarly, each eNB 102-103 could communicatedirectly with the network 130 and provide UEs with direct wirelessbroadband access to the network 130. Further, the eNB 101, 102, and/or103 could provide access to other or additional external networks, suchas external telephone networks or other types of data networks.

FIGS. 2A and 2B illustrate example wireless transmit and receive pathsaccording to the present disclosure. In the following description, atransmit path 200 can be described as being implemented in an eNB (suchas eNB 102), while a receive path 250 can be described as beingimplemented in a UE (such as UE 116). However, it will be understoodthat the receive path 250 could be implemented in an eNB and that thetransmit path 200 could be implemented in a UE. In some embodiments, thereceive path 250 is configured to receive and demodulate at least onetransmission with precoder cycling as well as support channel qualitymeasurement and reporting as described in embodiments of the presentdisclosure.

The transmit path 200 includes a channel coding and modulation block205, a serial-to-parallel (S-to-P) block 210, a size N Inverse FastFourier Transform (IFFT) block 215, a parallel-to-serial (P-to-S) block220, an add cyclic prefix block 225, and an up-converter (UC) 230. Thereceive path 250 includes a down-converter (DC) 255, a remove cyclicprefix block 260, a serial-to-parallel (S-to-P) block 265, a size N FastFourier Transform (FFT) block 270, a parallel-to-serial (P-to-S) block275, and a channel decoding and demodulation block 280.

In the transmit path 200, the channel coding and modulation block 205receives a set of information bits, applies coding (such asconvolutional, Turbo, or low-density parity check (LDPC) coding), andmodulates the input bits (such as with Quadrature Phase Shift Keying(QPSK) or Quadrature Amplitude Modulation (QAM)) to generate a sequenceof frequency-domain modulation symbols. The serial-to-parallel block 210converts (such as de-multiplexes) the serial modulated symbols toparallel data in order to generate N parallel symbol streams, where N isthe IFFT/FFT size used in the eNB 102 and the UE 116. The size N IFFTblock 215 performs an IFFT operation on the N parallel symbol streams togenerate time-domain output signals. The parallel-to-serial block 220converts (such as multiplexes) the parallel time-domain output symbolsfrom the size N IFFT block 215 in order to generate a serial time-domainsignal. The ‘add cyclic prefix’ block 225 inserts a cyclic prefix to thetime-domain signal. The up-converter 230 modulates (such as up-converts)the output of the ‘add cyclic prefix’ block 225 to an RF frequency fortransmission via a wireless channel. The signal can also be filtered atbaseband before conversion to the RF frequency.

A transmitted RF signal from the eNB 102 arrives at the UE 116 afterpassing through the wireless channel, and reverse operations to those atthe eNB 102 are performed at the UE 116. The down-converter 255down-converts the received signal to a baseband frequency, and theremove cyclic prefix block 260 removes the cyclic prefix to generate aserial time-domain baseband signal. The serial-to-parallel block 265converts the time-domain baseband signal to parallel time domainsignals. The size N FFT block 270 performs an FFT algorithm to generateN parallel frequency-domain signals. The parallel-to-serial block 275converts the parallel frequency-domain signals to a sequence ofmodulated data symbols. The channel decoding and demodulation block 280demodulates and decodes the modulated symbols to recover the originalinput data stream.

As described in more detail below, the transmit path 200 or the receivepath 250 can perform signaling for CSI reporting. Each of the eNBs101-103 can implement a transmit path 200 that is analogous totransmitting in the downlink to UEs 111-116 and can implement a receivepath 250 that is analogous to receiving in the uplink from UEs 111-116.Similarly, each of UEs 111-116 can implement a transmit path 200 fortransmitting in the uplink to eNBs 101-103 and can implement a receivepath 250 for receiving in the downlink from eNBs 101-103.

Each of the components in FIGS. 2A and 2B can be implemented using onlyhardware or using a combination of hardware and software/firmware. As aparticular example, at least some of the components in FIGS. 2A and 2Bcan be implemented in software, while other components can beimplemented by configurable hardware or a mixture of software andconfigurable hardware. For instance, the FFT block 270 and the IFFTblock 215 can be implemented as configurable software algorithms, wherethe value of size N can be modified according to the implementation.

Furthermore, although described as using FFT and IFFT, this is by way ofillustration only and should not be construed to limit the scope of thepresent disclosure. Other types of transforms, such as Discrete FourierTransform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions,could be used. It will be appreciated that the value of the variable Ncan be any integer number (such as 1, 2, 3, 4, or the like) for DFT andIDFT functions, while the value of the variable N can be any integernumber that is a power of two (such as 1, 2, 4, 8, 16, or the like) forFFT and IFFT functions.

Although FIGS. 2A and 2B illustrate examples of wireless transmit andreceive paths, various changes can be made to FIGS. 2A and 2B. Forexample, various components in FIGS. 2A and 2B could be combined,further subdivided, or omitted and additional components could be addedaccording to particular needs. Also, FIGS. 2A and 2B are meant toillustrate examples of the types of transmit and receive paths thatcould be used in a wireless network. Other suitable architectures couldbe used to support wireless communications in a wireless network.

FIG. 3A illustrates an example UE 116 according to the presentdisclosure. The embodiment of the UE 116 illustrated in FIG. 3A is forillustration only, and the UEs 111-115 of FIG. 1 could have the same orsimilar configuration. However, UEs come in a wide variety ofconfigurations, and FIG. 3A does not limit the scope of the presentdisclosure to any particular implementation of a UE.

The UE 116 includes an antenna 305, a radio frequency (RF) transceiver310, transmit (TX) processing circuitry 315, a microphone 320, andreceive (RX) processing circuitry 325. The UE 116 also includes aspeaker 330, a processor 340, an input/output (I/O) interface (IF) 345,an input 350, a display 355, and a memory 360. The memory 360 includesan operating system (OS) program 361 and one or more applications 362.

The RF transceiver 310 receives, from the antenna 305, an incoming RFsignal transmitted by an eNB of the network 100. The RF transceiver 310down-converts the incoming RF signal to generate an intermediatefrequency (IF) or baseband signal. The IF or baseband signal is sent tothe RX processing circuitry 325, which generates a processed basebandsignal by filtering, decoding, and/or digitizing the baseband or IFsignal. The RX processing circuitry 325 transmits the processed basebandsignal to the speaker 330 (such as for voice data) or to the processor340 for further processing (such as for web browsing data).

The TX processing circuitry 315 receives analog or digital voice datafrom the microphone 320 or other outgoing baseband data (such as webdata, e-mail, or interactive video game data) from the processor 340.The TX processing circuitry 315 encodes, multiplexes, and/or digitizesthe outgoing baseband data to generate a processed baseband or IFsignal. The RF transceiver 310 receives the outgoing processed basebandor IF signal from the TX processing circuitry 315 and up-converts thebaseband or IF signal to an RF signal that is transmitted via theantenna 305.

The processor 340 can include one or more processors or other processingdevices and execute the OS program 361 stored in the memory 360 in orderto control the overall operation of the UE 116. For example, processor340 could control the reception of forward channel signals and thetransmission of reverse channel signals by the RF transceiver 310, theRX processing circuitry 325, and the TX processing circuitry 315 inaccordance with well-known principles. In some embodiments, theprocessor 340 includes at least one microprocessor or microcontroller.

The processor 340 is also capable of executing other processes andprograms resident in the memory 360, such as operations for CQImeasurement and reporting for systems described in embodiments of thepresent disclosure as described in embodiments of the presentdisclosure. The processor 340 can move data into or out of the memory360 as required by an executing process. In some embodiments, theprocessor 340 is configured to execute the applications 362 based on theOS program 361 or in response to signals received from eNBs or anoperator. The processor 340 is also coupled to the I/O interface 345,which provides the UE 116 with the ability to connect to other devicessuch as laptop computers and handheld computers. The I/O interface 345is the communication path between these accessories and the processor340.

The processor 340 is also coupled to the input 350 (e.g., keypad,touchscreen, button etc.) and the display 355. The operator of the UE116 can use the input 350 to enter data into the UE 116. The display 355can be a liquid crystal display or other display capable of renderingtext and/or at least limited graphics, such as from web sites.

The memory 360 is coupled to the processor 340. Part of the memory 360could include a random access memory (RAM), and another part of thememory 360 could include a Flash memory or other read-only memory (ROM).

As described in more detail below, the UE 116 can perform signaling andcalculation for CSI reporting. Although FIG. 3A illustrates one exampleof UE 116, various changes can be made to FIG. 3A. For example, variouscomponents in FIG. 3A could be combined, further subdivided, or omittedand additional components could be added according to particular needs.As a particular example, the processor 340 could be divided intomultiple processors, such as one or more central processing units (CPUs)and one or more graphics processing units (GPUs). Also, while FIG. 3Aillustrates the UE 116 configured as a mobile telephone or smartphone,UEs could be configured to operate as other types of mobile orstationary devices.

FIG. 3B illustrates an example eNB 102 according to the presentdisclosure. The embodiment of the eNB 102 shown in FIG. 3B is forillustration only, and other eNBs of FIG. 1 could have the same orsimilar configuration. However, eNBs come in a wide variety ofconfigurations, and FIG. 3B does not limit the scope of the presentdisclosure to any particular implementation of an eNB. eNB 101 and eNB103 can include the same or similar structure as eNB 102.

As shown in FIG. 3B, the eNB 102 includes multiple antennas 370 a-370 n,multiple RF transceivers 372 a-372 n, transmit (TX) processing circuitry374, and receive (RX) processing circuitry 376. In certain embodiments,one or more of the multiple antennas 370 a-370 n include 2D antennaarrays. The eNB 102 also includes a controller/processor 378, a memory380, and a backhaul or network interface 382.

The RF transceivers 372 a-372 n receive, from the antennas 370 a-370 n,incoming RF signals, such as signals transmitted by UEs or other eNBs.The RF transceivers 372 a-372 n down-convert the incoming RF signals togenerate IF or baseband signals. The IF or baseband signals are sent tothe RX processing circuitry 376, which generates processed basebandsignals by filtering, decoding, and/or digitizing the baseband or IFsignals. The RX processing circuitry 376 transmits the processedbaseband signals to the controller/processor 378 for further processing.

The TX processing circuitry 374 receives analog or digital data (such asvoice data, web data, e-mail, or interactive video game data) from thecontroller/processor 378. The TX processing circuitry 374 encodes,multiplexes, and/or digitizes the outgoing baseband data to generateprocessed baseband or IF signals. The RF transceivers 372 a-372 nreceive the outgoing processed baseband or IF signals from the TXprocessing circuitry 374 and up-converts the baseband or IF signals toRF signals that are transmitted via the antennas 370 a-370 n.

The controller/processor 378 can include one or more processors or otherprocessing devices that control the overall operation of the eNB 102.For example, the controller/processor 378 could control the reception offorward channel signals and the transmission of reverse channel signalsby the RF transceivers 372 a-372 n, the RX processing circuitry 376, andthe TX processing circuitry 374 in accordance with well-knownprinciples. The controller/processor 378 could support additionalfunctions as well, such as more advanced wireless communicationfunctions. In some embodiments, the controller/processor 378 includes atleast one microprocessor or microcontroller.

The controller/processor 378 is also capable of executing programs andother processes resident in the memory 380, such as an OS. Thecontroller/processor 378 is also capable of supporting channel qualitymeasurement and reporting for systems having 2D antenna arrays asdescribed in embodiments of the present disclosure. In some embodiments,the controller/processor 378 supports communications between entities,such as web RTC. The controller/processor 378 can move data into or outof the memory 380 as required by an executing process.

The controller/processor 378 is also coupled to the backhaul or networkinterface 382. The backhaul or network interface 382 allows the eNB 102to communicate with other devices or systems over a backhaul connectionor over a network. The interface 382 could support communications overany suitable wired or wireless connection(s). For example, when the eNB102 is implemented as part of a cellular communication system (such asone supporting 5G or new radio access technology or NR, LTE, or LTE-A),the interface 382 could allow the eNB 102 to communicate with other eNBsover a wired or wireless backhaul connection. When the eNB 102 isimplemented as an access point, the interface 382 could allow the eNB102 to communicate over a wired or wireless local area network or over awired or wireless connection to a larger network (such as the Internet).The interface 382 includes any suitable structure supportingcommunications over a wired or wireless connection, such as an Ethernetor RF transceiver.

The memory 380 is coupled to the controller/processor 378. Part of thememory 380 could include a RAM, and another part of the memory 380 couldinclude a Flash memory or other ROM. In certain embodiments, a pluralityof instructions, such as a BIS algorithm is stored in memory. Theplurality of instructions are configured to cause thecontroller/processor 378 to perform the BIS process and to decode areceived signal after subtracting out at least one interfering signaldetermined by the BIS algorithm.

As described in more detail below, the transmit and receive paths of theeNB 102 (implemented using the RF transceivers 372 a-372 n, TXprocessing circuitry 374, and/or RX processing circuitry 376) performconfiguration and signaling for CSI reporting.

Although FIG. 3B illustrates one example of an eNB 102, various changescan be made to FIG. 3B. For example, the eNB 102 could include anynumber of each component shown in FIG. 3A. As a particular example, anaccess point could include a number of interfaces 382, and thecontroller/processor 378 could support routing functions to route databetween different network addresses. As another particular example,while shown as including a single instance of TX processing circuitry374 and a single instance of RX processing circuitry 376, the eNB 102could include multiple instances of each (such as one per RFtransceiver).

FIG. 4 illustrates example two-dimensional (2D) antenna arraysconstructed from 16 dual-polarized elements arranged in a 4×2 or 2×4rectangular format which can be utilized in various embodiments of thepresent disclosure. In this illustrative embodiment, the 2Ddual-polarized antenna port array includes M_(a) rows and N_(a) columnswhere (M_(a), N_(a))=(2,4) and (4,2). The embodiment of the 2Ddual-polarized antenna port array shown in FIG. 4 is for illustrationonly. Other embodiments of the 2D dual-polarized antenna port arraycould be used without departing from the scope of the presentdisclosure.

The example 2D dual-polarized antenna port array arrangement results ina total of 2M_(a)N_(a)=16 ports, each mapped to one CSI-RS port. Thethree indices 400, 410, and 420 are three examples in indexing the 16antenna ports as a means of mapping antenna ports to precoding matrixelements. For row-first indexing 400, antenna ports associated with thesame polarization group are indexed in a row-first manner regardless of(M_(a), N_(a)). For longer-first indexing 410, antenna ports associatedwith the same polarization group are indexed in a column-first mannerwhen M_(a)>N_(a), but row-first manner when M_(a)≤N_(a). Forshorter-first indexing 420, antenna ports associated with the samepolarization group are indexed in a row-first manner when M_(a)>N_(a),but column-first manner when M_(a)≤N_(a). Indexing 400 is thereforetermed row-first indexing while indexing 410 longer-first indexing andindexing 420 shorter-first indexing.

In these illustrative embodiments, both M_(a) and N_(a) can beconfigured by an eNB for a UE. In another example, rather than definingM_(a) and N_(a) as the number of rows and columns of the rectangulararray of ports or port pattern, respectively, these two parameters canbe defined as two-dimensional precoding codebook parameters. The valuesof M_(a) and N_(a) partly determine the manner in which a codebook(hence each precoding matrix element in the codebook) is mapped ontoantenna ports of a one- or two-dimensional antenna array. Thisconfiguration can be performed with and without signaling the totalnumber of antenna ports. When a UE is configured with a codebook, theseparameters can be included either in a corresponding CSI processconfiguration or NZP (non-zero-power) CSI-RS resource configuration.

In LTE systems, precoding codebooks are utilized for CSI reporting. Twocategories of CSI reporting modes are supported: PUSCH-based aperiodicCSI (A-CSI) and PUCCH-based periodic CSI (P-CSI). In each category,different modes are defined based on frequency selectivity of CQI and/orPMI, that is, whether wideband (one CSI parameter calculated for all the“set S subbands”) or subband (one CSI parameter calculated for each “setS subband”) reporting is performed. The supported CSI reporting modesare given in TABLE 1 and 2.

TABLE 1 CQI and PMI Feedback Types for PUSCH (Aperiodic) CSI ReportingModes PMI Feedback Type Single Multiple No PMI PMI PMI PUSCH CQIWideband Mode 1-2 Feedback (wideband CQI) Type UE Selected Mode 2-0 Mode2-2 (subband CQI) Higher Layer- Mode 3-0 Mode 3-1 Mode 3-2 configured(subband CQI)

TABLE 2 CQI and PMI Feedback Types for PUCCH (Periodic) CSI ReportingModes PMI Feedback Type No PMI Single PMI PUCCH CQI Wideband Mode 1-0Mode 1-1 Feedback Type (wideband CQI) UE Selected Mode 2-0 Mode 2-1(subband CQI)

In Rel.12 LTE, dual-stage precoding codebook enumerated with a first anda second PMI values (i₁ and i₂, respectively) are supported for 4 and 8antenna ports. The first PMI value i₁ is associated with a group of fourDFT beams/precoders. The second PMI value i₂, on the other hand, selectsone out of four beams/precoders indicated with i₁, along with QPSKco-phasing between two polarization groups.

In Rel.13 LTE, a flexible codebook structure which accommodates 2DCSI-RS port patterns is supported for ‘CLASS A’ eMIMO-Type with 8, 12,and 16 antenna ports, where not only (N₁,N₂) are configurable, but alsooversampling factors for both dimensions (O₁,O₂) and four types ofcodebook subset selections configured via RRC parameter codebook-Config.In addition, a single-stage beam selection codebook for 2, 4, or 8antenna ports is also supported for ‘CLASS B’ eMIMO-Type.

Based on the above codebook, a resulting precoding matrix can bedescribed in Equation 1. That is, the first stage precoder can bedescribed as a Kronecker product of a first and a second precodingvector (or matrix), which can be associated with a first and a seconddimension, respectively. This type is termed partial Kronecker Product(partial KP) codebook. The subscripts m and n in W_(m,n)(i_(m,n)) denoteprecoding stage (first or second stage) and dimension (first or seconddimension), respectively. Each of the precoding matrices W_(m,n) can bedescribed as a function of an index which serves as a PMI component. Asa result, the precoding matrix W can be described as a function of 3 PMIcomponents i_(1,1), i_(1,2), i₂. The first stage pertains to a long-termcomponent. Therefore, the first stage is associated with long-termchannel statistics such as angle-of-departure (AoD) profile and AoDspread. On the other hand, the second stage pertains to a short-termcomponent which performs selection, co-phasing, or any linear operationto the first component precoder W_(1,1)(i_(1,1))⊗W_(1,2)(i_(1,2)). Inthe present disclosure, A⊗B denotes the Kronecker product between twomatrices A and B. The precoder W₂ (i₂), therefore, performs a lineartransformation of the long-term component such as a linear combinationof a set of basis functions or vectors associated with the columnvectors of W_(1,1)(i_(1,1))⊗W_(1,2)(i_(1,2))).

$\begin{matrix}{{W( {i_{1,1},i_{1,2},i_{2}} )} = {\underset{\underset{W_{1}{({i_{1,1},i_{1,2}})}}{︶}}{( {{W_{1,1}( i_{1,1} )} \otimes {W_{1,2}( i_{1,2} )}} )}{W_{2}( i_{2} )}}} & ( {{Equation}\mspace{14mu} 1} )\end{matrix}$Here, a UE measures a CSI-RS in a subframe designated to carry CSI-RS,calculates a CSI (including PMI, RI, and CQI where each of these threeCSI parameters can include multiple components) based on themeasurement, and reports the calculated CSI to a serving eNB 102.

The above precoding description is especially suitable when the servingeNB transmits non-precoded CSI-RS (NP CSI-RS). That is, a cell-specificone-to-one mapping between CSI-RS port and TXRU (transceiver unit) isutilized. Here, different CSI-RS ports have the same wide beam width anddirection and hence generally cell wide coverage. This use case can berealized when the eNB configures the UE with ‘CLASS A’ eMIMO-Type whichcorresponds to NP CSI-RS. Other than CQI and RI, CSI reports associatedwith ‘CLASS A’ or ‘nonPrecoded’ eMIMO-Type include (assuming the partialKP design inherent in the Rel.13 codebook described above) athree-component PMI {i_(1,1), i_(1,2), i₂}.

Another type of CSI-RS applicable to FD-MIMO is beamformed CSI-RS (BFCSI-RS). For example, beamforming operation, either cell-specific orUE-specific, is applied on a non-zero-power (NZP) CSI-RS resource(including multiple ports). Here, at least at a given time/frequencyCSI-RS ports have narrow beam widths and hence not cell wide coverage,and (at least from the eNB perspective) at least some CSI-RSport-resource combinations have different beam directions. Thisbeamforming operation is intended to increase CSI-RS coverage orpenetration. In addition, when UE-specific beamforming is applied to aCSI-RS resource (termed the UE-specific or UE-specifically beamformedCSI-RS), CSI-RS overhead reduction can be obtained when NZP CSI-RSresources are allocated efficiently through resource sharing (pooling)for multiple UEs either in time domain (for instance, aperiodictransmission), beam domain (UE-specific beamforming), or dynamic CSI-RSresource (re)configuration. When a UE is configured to receive BF CSI-RSfrom a serving eNB, the UE can be configured to report PMI parametersassociated with W₂ (W_(2,1) and/or W_(2,2)) without W₁ (W_(1,1) and/orW_(1,2)) or, in general, associated with a single-stageprecoder/codebook. This use case can be realized when the eNB configuresthe UE with ‘CLASS B’ eMIMO-Type which corresponds to BF CSI-RS. Otherthan CQI and RI, CSI reports associated with ‘CLASS B’ or ‘beamformed’eMIMO-Type (with one CSI-RS resource and alternative codebook) include aone-component PMI n. Although a single PMI defined with respect to adistinct codebook, this PMI can be associated with the second-stage PMIcomponent of ‘CLASS A’/‘nonPrecoded’ codebooks i₂.

Therefore, given a precoding codebook (a set of precoding matricesW(i_(1,1), i_(1,2), i₂)), a UE measures a CSI-RS in a subframedesignated to carry CSI-RS, calculates/determines a CSI (including PMI,RI, and CQI where each of these three CSI parameters can includemultiple components) based on the measurement, and reports thecalculated CSI to a serving eNB. In particular, this PMI is an index ofa recommended precoding matrix in the precoding codebook. Similar tothat for the first type, different precoding codebooks can be used fordifferent values of RI. The measured CSI-RS can be one of the two types:non-precoded (NP) CSI-RS and beamformed (BF) CSI-RS. As mentioned, inRel.13, the support of these two types of CSI-RS is given in terms oftwo eMIMO-Types: ‘CLASS A’ (with one CSI-RS resource) and ‘CLASS B’(with one or a plurality of CSI-RS resources), respectively.

In scenarios where DL long-term channel statistics can be measuredthrough UL signals at a serving eNB, UE-specific BF CSI-RS can bereadily used. This is typically feasible when UL-DL duplex distance issufficiently small. When this condition does not hold, however, some UEfeedback is necessary for the eNB to obtain an estimate of DL long-termchannel statistics (or any of its representation thereof). To facilitatesuch a procedure, a first BF CSI-RS transmitted with periodicity T1 (ms)and a second NP CSI-RS transmitted with periodicity T2 (ms), whereT1≤T2. This approach is termed hybrid CSI-RS. The implementation ofhybrid CSI-RS is largely dependent on the definition of CSI process andNZP CSI-RS resource.

As discussed above, utilizing UE-specific BF CSI-RS reduces the numberof ports configured to each UE by applying beamforming on NP CSI-RS. Forinstance, a serving eNB can apply wideband beamforming on a 16-port NPCSI-RS to form a 2-port BF CSI-RS for a served UE. If each UE isconfigured with 2-port BF CSI-RS, the resulting total CSI-RS overhead isreduced when the number of co-scheduled UEs is less than 8—assuming thesame transmission rate for NP and BF CSI-RS. However, although not allthe served UEs require data transmission in every subframe, the numberof served UEs per cell tends to be much larger than 8. Due to theburstiness and stochasticity of data traffic, UE-specific BF CSI-RS usesor requires an efficient CSI-RS resource allocation mechanism to ensurethat the total CSI-RS overhead can be minimized or, conversely, thenumber of served UEs per cell can be maximized.

Therefore, there is a need to enable an efficient CSI-RS resourceallocation mechanism for UE-specific BF CSI-RS.

Terms such as ‘non-precoded’ (or ‘NP’) CSI-RS and ‘beamformed’ (or ‘BF’)CSI-RS are used throughout the present disclosure. The essence of thepresent disclosure does not change when different terms or names areused to refer to these two CSI-RS types. For example, ‘CSI-RS-A’ and‘CSI-RS-B’ can refer to or be associated with these two CSI-RS types.Essentially these two CSI-RS types are a first CSI-RS and a secondCSI-RS. In another example, CSI-RS resource type can be used todifferentiate those two modes of operation instead of CSI-RS type.CSI-RS resources associated with these two types of CSI-RS can bereferred to as ‘a first CSI-RS resource’ and ‘a second CSI-RS resource’,or ‘CSI-RS-A resource’ and ‘CSI-RS-B resource’. Subsequently, the labels‘NP’ and ‘BF’ (or ‘np’ and ‘bf’) are examples and can be substitutedwith other labels such as ‘1’ and ‘2’, or ‘A’ and ‘B’, or TYPE1 andTYPE2, or CLASS-A and CLASS-B. In another example, a MIMO type oreMIMO-Type which can be associated with CSI reporting operation can beused to differentiate those two modes of operation instead of CSI-RStype. For example, a UE is configured with a MIMO type or eMIMO-Typeassociated with CSI reporting behaviors and, in addition, CSImeasurement behaviors. Names of higher-layer or RRC parameters utilizedin this invention disclosure are example and illustrative. Other nameswhich serve same functionalities can be utilized.

The present disclosure includes at least four components: aperiodicCSI-RS (Ap-CSI-RS) mechanism, Ap-CSI-RS resource definition, Ap-CSI-RSresource selection or reconfiguration, and Ap-CSI-RS reference resourcedefinition. Each of the four components can be used either by itself(without the other component) or in conjunction with at least one of theother four components.

For the first component (that is, aperiodic CSI-RS mechanism), FIG. 5illustrates an example mechanism 500 for aperiodic CSI-RS (Ap-CSI-RS).Ap-CSI-RS is characterized by two primary features. First, a pool ofCSI-RS resources is defined and shared among multiple served UEs (510).A CSI-RS resource from this pool can be assigned to a UE only when theUE measures CSI (hence a resource can only be used when the resource isneeded). The UE needs to measure CSI when its associated serving eNBchooses to receive a CSI reporting calculated based on a most recentchannel. This leads to a second primary feature. Ap-CSI-RS assignment isdone in conjunction with an aperiodic CSI request from the serving eNBto a served UE (in this example, termed UE-k). Therefore, Ap-CSI-RSresource information is included in a DCI of an UL grant which containsan A-CSI request to UE-k in subframe n (520). Along with the A-CSIrequest, the Ap-CSI-RS itself, which is placed in the same DL subframe nas the A-CSI trigger and the Ap-CSI-RS resource information.Alternatively, the Ap-CSI-RS can be placed in another subframe followingsubframe n (at the expense of CSI reporting delay). In response to theCSI request and the Ap-CSI-RS resource information in subframe n(assuming that the Ap-CSI-RS is placed in subframe n), UE-k measures theassociated Ap-CSI-RS assigned by the eNB (530) and reports a requestedA-CSI in subframe n+L (540) where L is specified and can bescenario-dependent. For instance, a default value of L is 4 followingRel.13 LTE. This mechanism can be applied to both NP and UE-specific BFCSI-RS.

Although NP CSI-RS is cell-specific, its resource configuration isUE-specific. When used for NP CSI-RS, Ap-CSI-RS mechanism facilitates NPCSI-RS overhead reduction as the NP CSI-RS can be transmitted only whennecessary. In turn, a served UE is assigned a CSI-RS resource and canmeasure NP CSI-RS only when necessary (aperiodically) thereby reducingcomputational complexity and hence UE power consumption. If applied toNP CSI-RS, channel measurement restriction can be utilized together withclass A CSI reporting since CSI measurement (in time and frequency) isperformed within the subframe containing Ap-CSI-RS.

Likewise, Ap-CSI-RS facilitates CSI-RS overhead reduction when appliedto UE-specific BF CSI-RS. This is because UE-specific BF CSI-RS can betransmitted only when necessary thereby reducing the total CSI-RSoverhead across all UEs. In turn, a served UE is assigned a CSI-RSresource and can measure BF CSI-RS only when necessary (aperiodically)thereby reducing computational complexity and hence UE powerconsumption.

For the second component (that is, aperiodic CSI-RS resourcedefinition), since Ap-CSI-RS is transmitted and measured aperiodically(whenever required), an Ap-CSI-RS resource is not characterized bysubframe configuration which includes subframe offset and periodicity(as in the legacy CSI-RS resource). Instead, an Ap-CSI-RS resource ischaracterized by at least one of the following parameters: the number ofassigned CSI-RS ports, a set of CSI-RS port numbers, and a CSI-RSpattern configuration. The second and third parameters are described asfollows.

Regarding the second parameters, to define a set of CSI-RS port numbersassigned to a UE, a master set of (available) port numbers {Port₀,Port₀+1, . . . , Port₀+N_(PORT,MAX)−1} is needed. At least two optionsare available. A first option is to define a new master set of portswhere a previously unused value of Port₀ (so that any value in themaster set {Port₀, Port₀+1, . . . , Port₀+N_(PORT,MAX)−1} is alsopreviously unused) is chosen. For example, by choosing Port₀=200, amaster set of ports {200,201, . . . , 199+N_(PORT,MAX)}, different fromthe available CSI-RS ports in Rel.13 {15,16, . . . , 30}, is defined. Asecond option is to extend the existing CSI-RS ports (in Rel.13 LTE) bychoosing Port₀=15 and increase N_(PORT,MAX) beyond the current value of16 which results in a master set of CSI-RS ports {15, 16, . . . ,14+N_(PORT,MAX)}. The second option allows usage of the legacy CSI-RSports for Ap-CSI-RS whenever the ports are available.

For a given number of CSI-RS ports N_(PORT), an N_(PORT)-port CSI-RSresource can be specified in terms of a port subset of the master set{Port₀, Port₀+1, . . . , Port₀+N_(PORT,MAX)−1}. At least two options arepossible.

A first option for port subset selection follows the legacy Rel.13 LTEand assuming that the second master set option (see the previousparagraph), an N_(PORT)-port CSI-RS resource is always associated withport numbers {15, 16, . . . , 14+N_(PORT)}. That is, the first CSI-RSport number is always 15 and the assigned CSI-RS port numbers areconsecutive for any CSI-RS resource assignment. In this case, the set ofCSI-RS port numbers is fixed for a given number of CSI-RS ports.Therefore, there is no need to indicate or signal port subset selectionin Ap-CSI-RS resource configuration.

A second option for port subset selection which offers more flexibleresource allocation and increased number of resource configurations isto allow a CSI-RS resource configuration to be associated with portnumbers {Port(0), Port(1), . . . , Port(N_(PORT)−1)} where Port(i) canbe any port number taken from the master set. A constraint ofPort(i)<Port(k),i>k can be further imposed. As an example, antenna ports{17, 18, 21, 22} can be assigned to a UE for N_(PORT)=4. For a givenvalue of N_(PORT,MAX) and N_(PORT), a total of

$N_{cand} = \begin{pmatrix}N_{{PORT},{MAX}} \\N_{PORT}\end{pmatrix}$candidates for CSI-RS port subset selection are available. Thus, if portsubset selection is unrestricted, all these candidates are available.Alternatively, only a part of these available candidates can be used. Inthat case, a restricted subset of available candidates

$N_{cand} < \begin{pmatrix}N_{{PORT},{MAX}} \\N_{PORT}\end{pmatrix}$is used.

For this second port subset selection option, port subset selection isto be signaled and indicated in Ap-CSI-RS resource configuration. Forthis purpose, either a length-N_(PORT,MAX) bitmap (indicating which portnumbers are assigned to a UE) or a ┌log₂ N_(cand)┐-bit port subsetindicator can be used. The bitmap is applicable for either unrestrictedor restricted subset selection. The subset indicator, on the other hand,is suitable for restricted subset selection.

Regarding the third parameter, for a given number of CSI-RS portsN_(PORT), an N_(PORT)-port CSI-RS resource can also be specified interms of a T-F (time frequency) pattern configuration, termed CSIreference signal configuration in Table 6.10.5.2.1 of REF1, but referredto as pattern configuration in this disclosure. This patternconfiguration indicates locations of CSI-RS REs in time and frequencywithin a subframe. In the legacy Rel.12 LTE, this is indicated by a32-value RRC parameter resourceConfig-r10 or ‘CSI reference signalconfiguration’ in Table 6.10.5.2.1 of REF1).

Based on the above description of Ap-CSI-RS resource configuration, thefollowing example Ap-CSI-RS resource pooling procedure can be describedin a three-step procedure as follows. In a first step, a serving eNBstarts from a master set of N PORT,MAX CSI-RS antenna port numbers{Port₀, Port₀+1, . . . , Port₀+N_(PORT,MAX)−1}. In a second step, if thefirst option of port subset selection is utilized, an aperiodic CSI-RS(Ap-CSI-RS) resource is characterized with the number of CSI-RS portsN_(PORT) and a pattern configuration. If the second option of portsubset selection is utilized, an aperiodic CSI-RS (Ap-CSI-RS) resourceis characterized with the number of CSI-RS ports N_(PORT) a bitmap or anindicator associated with a set of antenna port numbers {Port(0),Port(1), . . . , Port(N_(PORT)−1)}, and a pattern configuration. In athird step, the serving eNB assigns (at least) one N_(PORT) CSI-RSresource to a served UE-k associated with the resource configuration inStep 2.

In addition to those three parameters, other configuration parameterscan be incorporated in CSI-RS resource configuration (as a part ofCSI-RS resource configuration) for aperiodic CSI-RS. Some examples aregiven as follows: energy-per-RE ratio relative to PDSCH; eMIMO-Type(either ‘nonPrecoded’/‘CLASS A’ or ‘beamformed’/‘CLASS B’); a parameterindicating whether the CSI-RS is NZP (non-zero-power) or ZP(zero-power); a parameter indicating whether the CSI-RS configuration isperiodic or aperiodic.

For the third component (that is, aperiodic CSI-RS resource selection orreconfiguration), at least three options are possible for signaling eachof the three parameters associated with CSI-RS resource configuration(number of antenna ports, T-F pattern configuration, and port subsetconfiguration). A first option is to use RRC signaling per UE to performsemi-static (re)configuration of CSI-RS resource. Several served UEs canbe configured to share a same CSI-RS resource assignment or haveoverlapping resource assignments. A second option is to use UL grant byincorporating the parameter in an associated DCI which carries A-CSIrequest (trigger). Therefore, CSI-RS resource configuration is signaleddynamically. A third option is to use either periodic or aperiodicresource (re)configuration using a similar principle to semi-persistentscheduling (SPS). That is, an UL grant is used to signal a reconfiguredCSI-RS resource assignment to a served UE-k. This CSI-RS resourceassignment can be accompanied with A-CSI request (trigger) or signaledby itself. This CSI-RS resource (re)configuration can either beperformed every X ms where X can be configured via RRC signaling, orinitiated with activation/deactivation procedure based on DL assignmentsor UL grants. If periodic resource reconfiguration is used, the value ofX can be chosen large such as in the order of 200-ms or 320-ms.

The third option allows a more dynamic resource reconfiguration (whichis not possible with the first option since RRC configuration incurslarge delay) without incurring large DL signaling overhead (which is thecase with the second option). Therefore, it allows a more efficientpooling of Ap-CSI-RS resources with reasonable DL signaling overhead. Toset up a UE for the third option, an RRC configuration similar to theone for SPS-ConfigDL (TS 36.331 REF5) can be used. Only a few parametersare applicable (for example, parameters similar tosemiPersistSchedIntervalDL and/or numberOfConfSPS-Processes).

Considering the aforementioned three signaling options, applicable toeach of the three parameters, TABLE 3-A and 3-B describe severalpossible combinations for the first and the second options of portsubset selection, respectively.

TABLE 3-A Options for DL signaling mechanism of CSI-RS resourceconfiguration with fixed port subset selection (Opt. 1) Signalingmechanism Alt No. antenna ports N_(PORT) T-F pattern configuration 1.1RRC signaling (semi-static) RRC signaling (semi-static) 1.2 RRCsignaling (semi-static) Every UL grant which carries A-CSI request(dynamic) 1.3 RRC signaling (semi-static) In one UL grant which carriesA-CSI request (dynamic, semi-persistent) per X ms (X = CSI-RS resourcereconfiguration periodicity) 2.2 Every UL grant which carries A-CSIEvery UL grant which carries A-CSI request (dynamic) request (dynamic)3.3 In one DL assignment or UL grant which In one DL assignment or ULgrant which carries A-CSI request (dynamic, semi- carries A-CSI request(dynamic, semi- persistent), e.g. per X ms (X = CSI-RS persistent), e.g.per X ms (X = CSI-RS resource reconfiguration periodicity) or resourcereconfiguration periodicity) or aperiodically aperiodically

TABLE 3-B Options for DL signaling mechanism of CSI-RS resourceconfiguration with flexible port subset selection (Opt. 2) Signalingmechanism Alt No. antenna ports N_(PORT) T-F pattern configuration$\begin{matrix}{{Port}\mspace{14mu}{subject}} \\\begin{Bmatrix}{{{Port}\mspace{11mu}(0)},{{Port}\mspace{11mu}(1)},\ldots\mspace{14mu},} \\{{Port}{\;\;}( {N_{PORT} - 1} )}\end{Bmatrix}\end{matrix}\quad$ 1.1.1 RRC signaling (semi- RRC signaling(semi-static) RRC signaling (semi-static) static) 1.1.2 RRC signaling(semi- RRC signaling (semi-static) Every UL grant which static) carriesA-CSI request (dynamic) 1.1.3 RRC signaling (semi- RRC signaling(semi-static) In one DL assignment or static) UL grant which carries A-CSI request (dynamic, semi-persistent), e.g. per X ms (X = CSI-RSresource reconfiguration periodicity) or aperiodically 1.2.1 RRCsignaling (semi- Every UL grant which RRC signaling (semi-static)static) carries A-CSI request (dynamic) 1.3.1 RRC signaling (semi- Inone DL assignment or RRC signaling (semi-static) static) UL grant whichcarries A- CSI request (dynamic, semi-persistent), e.g. per X ms (X =CSI-RS resource reconfiguration periodicity) or aperiodically 1.2.2 RRCsignaling (semi- Every UL grant which Every UL grant which static)carries A-CSI request carries A-CSI request (dynamic) (dynamic) 1.3.3RRC signaling (semi- In one DL assignment or In one DL assignment orstatic) UL grant which carries A- UL grant which carries A- CSI request(dynamic, CSI request (dynamic, semi-persistent), e.g. per Xsemi-persistent), e.g. per X ms (X = CSI-RS resource ms (X = CSI-RSresource reconfiguration periodicity) reconfiguration periodicity) oraperiodically or aperiodically 2.2.2 Every UL grant which Every UL grantwhich Every UL grant which carries A-CSI request carries A-CSI requestcarries A-CSI request (dynamic) (dynamic) (dynamic) 3.3.3 In one DLassignment or In one DL assignment or In one DL assignment or UL grantwhich carries UL grant which carries A- UL grant which carries A- A-CSIrequest (dynamic, CSI request (dynamic, CSI request (dynamic,semi-persistent), e.g. per semi-persistent), e.g. per Xsemi-persistent), e.g. per X X ms (X = CSI-RS ms (X = CSI-RS resource ms(X = CSI-RS resource resource reconfiguration reconfigurationperiodicity) reconfiguration periodicity) periodicity) or oraperiodically or aperiodically aperiodically

For each of the options in TABLE 3-A and 3-B, at least a CSI requestfield in the DCI of an UL grant (which includes an associated aperiodicCSI-RS) is needed to trigger A-CSI. The CSI request field can includeone or multiple bits where each bit is associated with a cell. Inaddition, Ap-CSI-RS parameter(s) which need to be configured dynamically(a subset of the number of ports, T-F pattern configuration, and/or portsubset) are also included in the DCI of the UL grant. Theseconfiguration parameters can be defined as separate parameters orjointly with the CSI request field.

When a UE is configured with K CSI-RS resources (or resourceconfigurations), one CSI request field (which can include one ormultiple bits) can be used for each of the K CSI-RS resources (orresource configurations). When k of these K CSI request fields are setto 1, CSI-RS associated with each of these k CSI-RS resources (orresource configurations) is transmitted in the DL subframe containingthe UL grant.

When a UE is configured with two (possibly different) eMIMO-Type setupsin one CSI process where each eMIMO-Type setup is associated with one ormore CSI-RS resources (or resource configurations), one CSI requestfield (which can include one or multiple bits) can be used for each ofthe two eMIMO-Type setups. When either one or both CSI request fieldsare set to 1, CSI-RS associated with each triggered eMIMO-Type setup istransmitted in the DL subframe containing the UL grant.

When a combination of semi-static (RRC signaling) and eithersemi-persistent or dynamic signaling is used (such as Opt. 1.1, 1.2, or1.3 in TABLE 3-A; Opt. 1.1.1, 1.1.2, 1.1.3, 1.2.1, 1.3.1, 1.2.2, or1.3.3 in TABLE 3-B), at least one (NZP or ZP) CSI-RS resourceconfiguration parameter is semi-statically configured and at least oneCSI-RS resource configuration parameter is either semi-persistently ordynamically configured. In this case, the semi-static CSI-RS resourceconfiguration effectively indicates that the UE is semi-staticallyconfigured with a plurality of (K_(A)) CSI-RS resources (where K_(A) isthe number of possible CSI-RS resources or resource configurationsassociated with the semi-statically configured parameters). The secondsignaling—either semi-persistent or dynamic—selects one CSI-RS resourceor a subset of CSI-RS resources from the K_(A) semi-staticallyconfigured CSI-RS resources. Therefore, instead of defining CSI-RSresources in terms of parameters, the semi-static (higher-layer or RRC)signaling can instead configure the UE a set of K_(A) CSI-RS resourcesand the semi-persistent or dynamic signaling can select one of out ofK_(A) CSI-RS resources. Each of these CSI-RS resources can either be NZPor ZP.

In the present disclosure, several embodiments of CSI-RS resource(re)configuration scheme (referred above as semi-persistent resourcereconfiguration) with at least one CSI-RS resource configurationparameter signaled using the third option are given. For each of thefollowing embodiments, when a UE is configured with a plurality of CSIprocesses or component carriers, one CSI-RS resource (re)configuration(activation/release or activation/deactivation) can be associated withone CSI process or component carrier. Alternatively, one CSI-RS resource(re)configuration (activation/release or activation/deactivation) can beassociated with a plurality of CSI processes or component carriers.Alternatively, one CSI-RS resource (re)configuration (activation/releaseor activation/deactivation) can be associated with all the CSI processesor component carriers.

In a first embodiment (embodiment 1.A), anactivation-release/deactivation mechanism similar to semi-persistentscheduling is utilized to reconfigure CSI-RS resource. In thisembodiment, UL grants or DL assignments on PDCCH or EPDCCH are used toreconfigure CSI-RS resource. Therefore, an UL grant or DL assignmentused for this purpose includes at least one DCI field either forselecting one out of multiple choices of CSI-RS resource configuration(which are, for instance, configured via higher layer signaling as apart of CSI-RS resource configuration ASN.1 Information Element) or forsetting the value of at least one CSI-RS resource configurationparameter. This field can be a part of an existing DCI format (such asDCI format 0 or 4 for UL grant, or format 1A, 2/2A/2B for DL assignment)or a new DCI format specifically designed for CSI-RS resourcereconfiguration (activation/release or activation/deactivation). The ULgrant (or DL assignment) is signaled to the UE via PDCCH or EPDCCH andmasked by a special RNTI (such as CSI-RNTI).

FIG. 6 describes an example eNB and UE operations 600 (in terms oftiming diagram associated with eNB in 601 and UE in 602) when at leastone CSI-RS resource configuration parameter is signaled using the thirdoption. For example, this corresponds to Opt. 1.3 or 3.3 in TABLE 3-A,or Opt. 1.1.3, 1.3.1, 1.3.3, or 3.3.3 in TABLE 3-B. In this embodiment,Ap-CSI-RS resource is reconfigured every X ms in subframe(s) 610 via anUL grant (or an UL-related grant or, alternatively, a DL assignment)which carries Ap-CSI-RS resource configuration information (includingthe DCI field mentioned above). This configuration information can beaccompanied with an A-CSI request/trigger or signaled by itself. Uponreceiving a DL subframe from 610, a served UE-k reads the configurationinformation in 630. Based on this configuration information, the eNBrequests A-CSI to UE-k via an UL grant (containing A-CSI trigger) whiletransmitting Ap-CSI-RS within the same subframe(s) 620. Upon receiving aDL subframe from 640—containing an A-CSI request/trigger—UE-k measuresthe transmitted Ap-CSI-RS (in subframe n) according to the resourceconfiguration information received in subframe(s) 630, and performs CSIcalculation. The resulting A-CSI is reported to the eNB in subframe(s)650. In the example in FIG. 6, the semi-persistently configured CSI-RSresource includes a set of the number of ports.

Although the above example assumes periodic resource reconfiguration(every X ms), aperiodic resource reconfiguration using activation anddeactivation based on UL grant or DL assignment can also be used.

The above semi-persistent CSI-RS resource allocation mechanism, appliedto NZP CSI-RS resource, can be described as follows. First, a UEreceives a dynamic trigger/release containing a selection from multiplehigher-layer-configured NZP CSI-RS resources. These multiple CSI-RSresources can be associated with a first set of configured parameters(set values of CSI-RS resource configuration parameters) or simply alist of K_(A) CSI-RS resources. Likewise, dynamic trigger or release canindicate either a ┌log(K_(A))┐-bit DCI field or another set ofparameters which, together with the first parameter set, furtherindicates the selected CSI-RS resource. In this embodiment, each NZPCSI-RS resource can be either periodic or aperiodic CSI-RS resource.Second, for an activation trigger received in subframe n, thetransmission of the associated NZP CSI-RS resource will start no earlierthan subframe n+Y1 where Y1>0. Third, for a release (deactivation)trigger received in subframe n, the transmission of the associated NZPCSI-RS resource will stop after subframe n+Y1 where Y1>0. Fourth, if anUL grant or UL grant-like mechanism is used to trigger CSI-RS which isplaced or transmitted in a same subframe as the UL grant, the value ofY1 or Y2 can be aligned with that of A-CSI. The same holds if a DL grantis used instead.

In a second embodiment (embodiment 1.B), anactivation-release/deactivation mechanism (similar to semi-persistentscheduling) is also utilized to reconfigure CSI-RS resource, but insteadof using PDCCH, MAC control element (MAC CE) is used. Here, a new typeof MAC CE can be defined for the purpose of reconfiguring CSI-RSresource. For example, this type of MAC CE can be termed “CSI-RSresource reconfiguration MAC control element (MAC CE)”. For each of thefollowing embodiments using MAC CE, when a UE is configured with aplurality of CSI processes or component carriers, one CSI-RS resourceactivation/release can be associated with one CSI process or componentcarrier. Alternatively, one CSI-RS resource activation/release can beassociated with a plurality of CSI processes or component carriers.Alternatively, one CSI-RS resource activation/release can be associatedwith all the CSI processes or component carriers.

This CSI-RS resource reconfiguration MAC CE is signaled to the UE viaDL-SCH and included in a MAC PDU. Since the number of CSI-RS resourceconfiguration parameters (as well as the length of each parameter)included in the MAC CE remains the same, the size of CSI-RS resourcereconfiguration MAC CE can be fixed. Therefore, its associated MAC PDUsub-header includes solely of the 4 header fields R/F2/E/LCID (cf. REF4section 6.1.2). The arrangement of CSI-RS resource configuration MAC CEcan be illustrated in diagram 700 of FIG. 7A where MAC CE 1 (701) isdesignated as a CSI-RS resource configuration MAC CE and associated withMAC PDU sub-header 702. The 5-bit LCID (logical channel ID) indicatesthe type of logical channel. In this case, CSI-RS resource configurationMAC CE can utilize any of the reserved hypotheses (within01011-10111-cf. Table 6.2.1-1 of REF4).

An example of a MAC CE design for CSI-RS resource reconfiguration is asfollows. First, the MAC CE design includes at least one CSI-RS resourceconfiguration parameter, each written as a binary (bit) sequence andarranged in an octet-aligned format. For instance, if all the threeparameters mentioned above (number of ports, T-F pattern, and portnumber set) are configurable via a MAC CE, three fields are included inthe CSI-RS resource configuration MAC CE. This is illustrated in diagram750 of FIG. 7B where three fields 752 (number of CSI-RS ports N_(PORT),2 bits—4 hypotheses), 753 (T-F pattern, 5 bits—32 hypotheses), and 754(port number set, 8 bits—up to 256 hypotheses) are included in a MAC CEwith a fixed size of two octets. A one-bit reserved field R (751) isadded at the beginning to fit the three fields into a two-octetcodeword. Alternatively, if port number set is not needed (for instance,configured via higher layer signaling, or simply fixed to {15, 16, . . ., 14+N_(PORT)}), only one octet may be needed.

The above semi-persistent CSI-RS resource allocation schemes (the firstand the second embodiments) can also be used for ZP CSI-RS resource.

The above semi-persistent CSI-RS resource allocation schemes (the firstand the second embodiments are used and applicable for aperiodic CSI-RS.Alternatively, these first and the second embodiments can also beapplied to periodic CSI-RS (that which is associated with subframeconfiguration in CSI-RS resource configuration—such as subframe offsetand periodicity). When applied to periodic CSI-RS, each of the twoschemes can be used to start/activate or stop/deactivate CSI-RSmeasurement at a UE. For the first embodiment, a DCI field in an ULgrant or a DL assignment is used to signal the start or the stop of CSImeasurement associated with a selected CSI-RS resource. For the secondembodiment, the CSI-RS resource reconfiguration MAC CE is used to signalthe start or the stop of CSI measurement associated with a selectedCSI-RS resource.

For either embodiment (1.A or 1.B), two possibilities exist. First, thesize and content of the DCI field (first embodiment) or MAC CE (secondembodiment) can be different from that used for aperiodic CSI-RS. Inthis case, the selected CSI-RS resource is configured for the UE viahigher layer signaling. Therefore, the DCI field (first embodiment) orthe MAC CE (second embodiment) simply signals START (activate) or STOP(deactivate). Second, the size and content of the DCI field (firstembodiment) or MAC CE (second embodiment) are identical to that used foraperiodic CSI-RS. In this case, the selected CSI-RS resource isindicated in the DCI field (first embodiment) or the MAC CE (secondembodiment)—selected out of a plurality of (K_(A)) resources which areconfigured for the UE via higher-layer signaling—in the same manner asthat for aperiodic CSI-RS (cf. FIGS. 7A and 7B).

For Ap-CSI-RS, several schemes exist in designing higher-layer (such asRRC) CSI-RS resource configuration.

In a first scheme, Rel.13 CSI-RS resource configuration (based onperiodic CSI-RS resource configuration) is reused but unusedconfiguration parameters such as CSI-RS subframe configuration(periodicity and subframe offset) are ignored when the CSI-RS resourceis configured as aperiodic. For this embodiment, a parameter whichindicates whether the CSI-RS resource is periodic or aperiodic (orwhether aperiodic is ON) can be added inside the CSI-RS resourceconfiguration information. This embodiment can be described in thefollowing example ASN.1 setup in TABLE 4-A when the number of antennaports and T-F pattern (resourceConfig) are configured semi-staticallyvia RRC signaling. When CSI-RS-Alloc-r14 is set as {aperiodic},subframeConfig-r10 is unused.

TABLE 4-A CSI-RS-Config-r10 ::= SEQUENCE {   csi-RS-r10   CHOICE {    release     NULL,     setup   SEQUENCE {       antennaPortsCount-r10ENUMERATED {an1, an2, an4, an8},       resourceConfig-r10 INTEGER(0..31),       subframeConfig-r10 INTEGER (0..154),       p-C-r10INTEGER (−8..15)       CSI-RS-Alloc-r14   ENUMERATED {periodic,aperiodic} OPTIONAL  -- Need OR     }   }       OPTIONAL,   -- Need ON  zeroTxPowerCSI-RS-r10   ZeroTxPowerCSI-RS-Conf-r12    OPTIONAL   --Need ON }

In a second scheme, a new CSI-RS resource configuration for aperiodicCSI-RS is used. For this embodiment, a parameter which indicates whetherthe CSI-RS resource is periodic or aperiodic (or whether aperiodic isON) can be added to select between the legacy Rel.13 CSI-RS resourceconfiguration (based on periodic CSI-RS resource configuration) andaperiodic CSI-RS resource configuration. This embodiment can bedescribed in the example ASN.1 setup in TABLE 4-B when the number ofantenna ports and T-F pattern (resourceConfig) are configuredsemi-statically via RRC signaling. In this case, either port subset isnot configurable or configured dynamically or semi-dynamically. Tochoose between the legacy periodic CSI-RS resource configuration and theaperiodic CSI-RS configuration, a parameter aperiodic CSI-RS-r14 is usedin the example description in TABLE 4-C.

TABLE 4-B CSI-RS-Config-Ap-r14 ::= SEQUENCE {   csi-RS-Ap-r14   CHOICE {    release   NULL,     setup SEQUENCE {       antennaPortsCount-r10ENUMERATED {an1, an2, an4, an8},       resourceConfig-r10 INTEGER(0..31),       p-C-r10 INTEGER (−8..15)     }   }          OPTIONAL,    -- Need ON   zeroTxPowerCSI-RS-Ap-r14  ZeroTxPowerCSI-RS- Ap-Conf-r14   OPTIONAL    -- Need ON }

TABLE 4-C CSI-RS-Config-v14 ::=  SEQUENCE {    eMIMO-Type-r13 CSI-RS-ConfigEMIMO-r13    OPTIONAL -- Need ON   CSI-RS-Alloc-r14CSI-RS-Config-PvAp-r14     OPTIONAL -- Need ON } CSI-RS-Config-PvAp-r14::= CHOICE {    release NULL,    setup  CHOICE {     periodic CSI-RS-Config-r10,     aperiodic  CSI-RS-Config-Ap-r14    } }

In a third scheme, when a UE is configured with a plurality of CSI-RSresources (or resource configurations) in one CSI process, one selectionparameter (between periodic and aperiodic CSI-RS resource configuration)can be introduced for each of the plurality of CSI-RS resources (orresource configurations). That is, each CSI-RS resource (or resourceconfiguration) can be configured either as a periodic or an aperiodicCSI-RS resource.

In a fourth scheme, the selection parameter (between periodic andaperiodic CSI-RS resource configuration) can be introduced in the CSIprocess configuration. Therefore, if one CSI process is configured witha plurality of CSI-RS resources (or resource configurations), all orsome of the CSI-RS resources (or resource configurations) associatedwith the CSI process share a same CSI-RS resource allocation (eitherperiodic or aperiodic).

In a fifth scheme, when a UE is configured with two (possibly different)eMIMO-Type setups in one CSI process where each eMIMO-Type setup isassociated with one or more CSI-RS resources (or resourceconfigurations), one selection parameter (between periodic and aperiodicCSI-RS resource configuration) can be introduced for each of the twoeMIMO-Type setups. Therefore, if one of the eMIMO-Type setups isconfigured with a plurality of CSI-RS resources (or resourceconfigurations), all or some of the CSI-RS resources (or resourceconfigurations) associated with the eMIMO-Type setup share a same CSI-RSresource allocation (either periodic or aperiodic).

In a sixth scheme, a parameter which indicates whether the CSI-RSresource is periodic or aperiodic (or whether aperiodic is ON) can beadded inside the (higher-layer) configuration for aperiodic CSIreporting. This can be described in the example ASN.1 setup in TABLE4-D. The parameter CSI-RS-Alloc-r14 configures the UE to measure eitherperiodic or aperiodic CSI-RS for the configured A-CSI reporting.

TABLE 4-D CQI-ReportAperiodic-r10 ::= CHOICE {   release   NULL,   setupSEQUENCE {     CSI-RS-Alloc-r14  ENUMERATED {periodic, aperiodic}OPTIONAL  -- Need OR     cqi-ReportModeAperiodic-r10   CQI-ReportModeAperiodic,     aperiodicCSI-Trigger-r10    SEQUENCE {      trigger1-r10  BIT STRING (SIZE (8)),       trigger2-r10  BITSTRING (SIZE (8))     }          OPTIONAL -- Need OR   } }

In a third embodiment (embodiment 1.C), CSI-RS resource configuration orreconfiguration can include a combination between semi-static CSI-RSresource configuration, activation/deactivation CSI-RS resourceconfiguration, and dynamic CSI-RS resource selection. This embodiment isillustrated in diagram 800 of FIG. 8A. In this embodiment, an initial(first-step) CSI-RS resource configuration is performed in step 810where a UE is configured with an aperiodic CSI-RS resource viahigher-layer (RRC) signaling. In this initial resource configuration, aset of K NZP CSI-RS resources is defined or configured for the UE. Thisset of resources can be described by setting at least one CSI-RSresource parameter to a certain value (while not setting value for otherCSI-RS resource parameters). Alternatively, the set of resources can bedescribed by listing K combinations of values of a plurality of CSI-RSresource parameters.

A second-step CSI-RS resource configuration is performed in step 820where a UE is configured with an aperiodic CSI-RS resource viaactivation/deactivation (activation/release) procedure using MAC controlelement (CE) signaling or UL-related DCIs (UL grants) or DL-related DCIs(DL grants)—as detailed above. In this initial resource configuration, aset of K_(A)<K NZP CSI-RS resources is defined or configured for the UE.This set of resources (or resource configurations) can be described bysetting at least one CSI-RS resource parameter to a certain value (whichare not set in the first step, while not setting value for otherremaining CSI-RS resource parameters). Alternatively, the set ofresources can be described by listing K_(A) combinations of values of aplurality of CSI-RS resource parameters taken from a size-K_(A) subsetof K resources defined or given in the first step.

Diagram 850 FIG. 8B depicts an example of MAC CE signaling where asize-K_(A) subset of K CSI-RS resources is selected and activated for aUE. Therefore, the number of used or required hypotheses or code pointsis

$\quad\begin{pmatrix}K \\K_{A}\end{pmatrix}$which can be signaled with

$\lceil {\log_{2}\begin{pmatrix}K \\K_{A}\end{pmatrix}} \rceil - {bit}$codeword. In this example, for illustrative purposes, K and K_(A) areset to be 8 and 4, respectively, which result in a 7-bit codeword(852)—appended with 1 reserved bit (851) to form an octet. In anotherexample where K and K_(A) are set to be 8 and 2, respectively, whichresult in a 5-bit codeword and a 3 reserved bits. In general, the numberof bits for the CSI-RS resource subset selection field can be fixed tothe worst-case (maximum) value or can be made dependent on either K,K_(A), or both K and K_(A).

The value of K can be configured via higher-layer signaling within aCSI-RS resource configuration. For example, this CSI-RS resourceconfiguration can be an aperiodic CSI-RS resource configurationassociated with CLASS B eMIMO-Type. Each of these K NZP CSI-RS resourcesis associated with a set of CSI-RS resource parameters such as T-F(time-frequency) pattern (5-bit resourceConfig in REF5, CSI ReferenceSignal Configuration in REF1), number of ports N_(PORT) ∈{1,2,4,8}(antennaPortsCount in REF5), pC, and/or other parameters. Each of theseK NZP CSI-RS resources is not associated with any subframe configurationparameters (such as periodicity and subframe offset).

The value of K_(A) can be fixed. For example, the value can be fixed to4 or 2.

The value of K_(A) can also be made configurable. An example is thatK_(A) can take value from the set {1, 2, . . . , min(K, K_(A,MAX))}where K_(A,MAX) can either be fixed (to, e.g. 4 or 2) or made dependenton UE capability. Another example is that K_(A)=K when K≤2; and K_(A)can take value from the set {1, 2, . . . , min(K, K_(A,MAX))} whereK_(A,MAX) can either be fixed (to, e.g. 4 or 2) or made dependent on UEcapability when K>2.

When K=1 or K_(A)=K, this second-step is by definition skipped.

The value of K_(A) can be configured via higher-layer signaling. Forinstance, an RRC parameter K_(A) can be defined in association or as apart of an aperiodic CSI-RS resource configuration. Alternatively, K_(A)can be defined in association or as a part of the (CLASS B) eMIMO-Typeinformation element. Alternatively, K_(A) can be defined in associationor as a part of the aperiodic CSI reporting configuration.

Alternatively, instead of signaling K_(A) via higher-layer (RRC)signaling, K_(A) can be signaled via MAC CE. This can be done in atleast two manners. First, the value of K_(A) is explicitly signaledtogether with CSI-RS resource subset selection as depicted in diagram860 of FIG. 8C. In this example, CSI-RS resource subset selection field(862) is signaled together with the value of K_(A) (863). One reservedbit is added (861) for illustrative purposes. If the total number ofbits for 862 and 863 exceeds 8, two octets can be used. In general, thenumber of bits for the CSI-RS resource subset selection field can befixed to the worst-case (maximum) value or can be made dependent on thevalue of K.

Another variation of this embodiment is illustrated in diagram 870 ofFIG. 8D where a length-K bitmap B_(K-1) B_(K-2) . . . B₁B₀ is used. Inthis illustrative embodiment, the value of K is 8. If K is less than 8,(8−K) reserved bits can be appended. Here, the k-th bit denotes whetherthe k-th CSI-RS resource (out of the K higher-layer-configured CSI-RSresources) is activated or dormant. In particular, when B_(k)=0, thek-th CSI-RS resource is dormant (not activated). When B_(k)=1, the k-thCSI-RS resource is activated. In this case, the number of B_(k) whosevalue(s) are 1 is equal to K_(A). Therefore, the value of K_(A) isimplicitly signaled in the bitmap 871 and variable (configurable via MACCE). An example is that K_(A) (the number of B_(k) whose value(s) are 1)can take value from the set {1, 2, . . . , min(K, K_(A,MAX))} whereK_(A,MAX) can either be fixed (to, e.g. 4 or 2) or made dependent on UEcapability. Another example is that K_(A)=K when K≤2; and K_(A) (thenumber of B_(k) whose value(s) are 1) can take value from the set {1, 2,. . . , min(K, K_(A,MAX))} where K_(A,MAX) can either be fixed (to, e.g.4 or 2) or made dependent on UE capability when K>2.

If UL-related DCIs (UL grants) or DL-related DCIs (DL grants) are usedfor activation/release, the mechanism can be described as follows.First, a UE receives a dynamic trigger/release UL or DL grant indicatinga selection/activation size-K_(A) subset of K NZP CSI-RS resources. Thisselection corresponds to a

$\lceil {\log_{2}\begin{pmatrix}K \\K_{A}\end{pmatrix}} \rceil - {bit}$DCI field. Alternatively, at least one of these

$\quad\begin{pmatrix}K \\K_{A}\end{pmatrix}$code points (hypotheses) can be signaled using some available (unused)or reserved code points in the DCI, while other code points (hypotheses)can be signaled using at least one additional bit in the DCI. Thissubset selection indicates that the associated size—K_(A) subset of KNZP CSI-RS resources are activated and the UE shall measure or monitor(be ready to measure) these NZP CSI-RS resources. In this embodiment,each NZP CSI-RS resource can be either periodic or aperiodic CSI-RSresource. Second, for an activation trigger received in subframe n, thetransmission of the associated NZP CSI-RS resource will start no earlierthan subframe n+Y1 where Y1>0. For a release (deactivation) triggerreceived in subframe n, the transmission of the associated NZP CSI-RSresource will stop after subframe n+Y1 where Y1>0. If an UL grant or ULgrant-like mechanism is used to trigger CSI-RS which is placed ortransmitted in a same subframe as the UL grant, the value of Y1 or Y2can be aligned with that of A-CSI. The same holds if a DL grant is usedinstead.

To perform activation and release, either the MAC-CE-based or theUL/DL-grant-based mechanism (as described above), at least the followingprocedures are possible. The interpretation of the currently receivedvalue of ‘Activation Subset’ (indication of size-K_(A) subset of K NZPCSI-RS resources) can either depend on the most recent previouslyreceived one or independent of the most recent previously received one.

In a first procedure (P-1), if a UE receives a CSI-RS MAC CE indicatingthe ‘Activation Subset’=x, or a UL/DL activation/release grant whose DCIincludes the ‘Activation Subset’ (indication of size-K_(A) subset of KNZP CSI-RS resources)=x, this can be interpreted as follows. If the mostrecent previously received CSI-RS MAC CE or the DCI of the most recentpreviously received UL/DL activation/release grant includes the‘Activation Subset’=x (the same as the currently received one), thecorresponding size-K_(A) subset of K NZP CSI-RS resources activated bythe previous activation/release event are released. If the most recentpreviously received CSI-RS MAC CE or the DCI of the most recentpreviously received UL/DL activation/release grant includes the‘Activation Subset’=y≠x (different from the currently received one), thesize-K_(A) subset of K NZP CSI-RS resources corresponding to ‘ActivationSubset’=x are activated (and, consequently, the size-K_(A) subset of KNZP CSI-RS resources corresponding to ‘Activation Subset’=y are alsostill activated). If there is no previously received CSI-RS MAC CE orUL/DL activation/release grant, the corresponding size-K_(A) subset of KNZP CSI-RS resources are activated.

In a second procedure (P-2), if a UE receives a CSI-RS MAC CE indicatingthe ‘Activation Subset’=x, or a UL/DL activation/release grant whose DCIincludes the ‘Activation Subset’ (indication of size-K_(A) subset of KNZP CSI-RS resources)=x, this can be interpreted as follows. If the mostrecent previously received CSI-RS MAC CE or the DCI of the most recentpreviously received UL/DL activation/release grant includes the‘Activation Subset’=x (the same as the currently received one), thesize-K_(A) subset of K NZP CSI-RS resources corresponding to ‘ActivationSubset’=x are still activated/active. If the most recent previouslyreceived CSI-RS MAC CE or the DCI of the most recent previously receivedUL/DL activation/release grant includes the ‘Activation Subset’=y≠x(different from the currently received one), the size-K_(A) subset of KNZP CSI-RS resources corresponding to ‘Activation Subset’=x areactivated (and, consequently, the size-K_(A) subset of K NZP CSI-RSresources corresponding to ‘Activation Subset’=y are released). If thereis no previously received CSI-RS MAC CE or UL/DL activation/releasegrant, the corresponding size-K_(A) subset of K NZP CSI-RS resources areactivated.

In a third procedure (P-3), two additional code points (hypotheses) canbe used to indicate either ‘Activation’ or ‘Release’/‘Deactivation’. Ifa UE receives a CSI-RS MAC CE indicating the ‘Activation Subset’=x, or aUL/DL activation/release grant whose DCI includes the ‘ActivationSubset’ (indication of size-K_(A) subset of K NZP CSI-RS resources)=x,this can be interpreted as follows. If ‘Activation’ is indicated, thesize-K_(A) subset of K NZP CSI-RS resources corresponding to ‘ActivationSubset’=x are activated. If ‘Release’ or ‘Deactivation’ is indicated,the size-K_(A) subset of K NZP CSI-RS resources corresponding to‘Activation Subset’=x are released.

In the first and the third procedures (P-1 and P-3), once a size-K_(A)subset of K NZP CSI-RS resources is activated, the size-K_(A) subset ofK NZP CSI-RS resources will remain activated until arelease/deactivation (either via two consecutive identical values ofsize-K_(A) subset of K NZP CSI-RS resources) associated with the samesize-K_(A) subset of K NZP CSI-RS resources is received. In the secondprocedure (P-2), once a size-K_(A) subset of K NZP CSI-RS resources isactivated, the size-K_(A) subset of K NZP CSI-RS resources will remainactivated until another activation message including a size-K_(A) subsetof K NZP CSI-RS resources different from the previous one is received.In all or some of the three procedures (P-1, P-2, and P-3), more thanone size-K_(A) subset of K NZP CSI-RS resources can be activated withina given subframe. In the second procedure (P-2), it is possible for a UEnot to have any size-K_(A) subset of K NZP CSI-RS resources activated ina given subframe. In the first and third procedures (P-1 and P-3), atleast one size-K_(A) subset of K NZP CSI-RS resources activated in agiven subframe.

Diagram 900 of FIG. 9 illustrates an example eNB and UE operations (interms of timing diagram associated with eNB in 901 and UE in 902) whichapplies to either the MAC-CE-based or the UL/DL-grant-based mechanism.In this embodiment, an activation/release message containing ‘ActivationSubset’ 910 is received by a UE. This configuration information can beaccompanied with an A-CSI request/trigger or signaled by itself. Uponreceiving a DL subframe from 910, a served UE-k reads theactivation/release message in 930. Based on this information, the eNBrequests A-CSI to UE-k via an UL grant (containing A-CSI trigger) whiletransmitting Ap-CSI-RS within the same subframe(s) 920. Upon receiving aDL subframe from 940—containing an A-CSI request/trigger—UE-k measuresthe transmitted Ap-CSI-RS (in subframe n) according to the resourceconfiguration information received in subframe(s) 930, and performs CSIcalculation. The resulting A-CSI is reported to the eNB in subframe(s)950.

For each of the above embodiments for selecting/activating a size-K_(A)subset of K NZP CSI-RS resources using MAC CE, when a UE is configuredwith a plurality of CSI processes or component carriers, one CSI-RSresource activation/release can be associated with one CSI process orcomponent carrier. Alternatively, one CSI-RS resource activation/releasecan be associated with a plurality of CSI processes or componentcarriers. Alternatively, one CSI-RS resource activation/release can beassociated with all the CSI processes or component carriers.

In a third step illustrated in component 830 of FIG. 8A, a UE isassigned one Ap-CSI-RS transmission wherein the CSI-RS resourceconfiguration is selected from K_(A) configurations given in the secondstep. This selected resource (or resource configuration) can bedescribed by setting at least one CSI-RS resource parameter to a certainvalue (which are not set in the first and second steps). Alternatively,the selected resource can be described by indicating one combination ofvalues of a plurality of CSI-RS resource parameters taken from asize-K_(A) combination of values of a plurality of CSI-RS resourceparameters defined or given in the second step. This selection issignaled via the UL-related DCI (included in the UL grant) used for CSIrequest (A-CSI triggering)—either via PDCCH or EPDCCH.

The following examples can be constructed assuming that the number ofCSI-RS ports N_(PORT) is configured semi-statically (the first step, viahigher-layer signaling) while a set of time-frequency patterns (known as“CSI reference signal configuration” in REF1) can be configured usingactivation/deactivation procedure (the second step). The set of portindices is not configurable. That is, for an N_(PORT) port CSI-RS, theset of port indices is always {15, 16, . . . , 14±N_(PORT)}.

In a first example, the number of CSI-RS ports N_(PORT) is included asan RRC parameter (such as ‘antennaPortsCount’) in the RRC configurationIE ‘CSI-RS-Config’ along with other CSI-RS parameters (such as pC)except for the time-frequency pattern ‘resourceConfig’. For aperiodicCSI-RS, subframe configuration is not present. In the second step, a setof K_(A) values of ‘resourceConfig’, where K_(A)=2, is configured viaactivation/deactivation mechanism. That is, 2 out of 32 possible valuesof ‘resourceConfig’ are selected for the UE in the second-step CSI-RSresource configuration. For this purpose, a 10-bit (5 bits per value)field is needed to signal the selection, either in a MAC CE (cf. examplein FIG. 7A, where the MAC CE includes ‘resourceConfig’) or a DCI usedfor activation/deactivation. In the third step, one additional bit (perCSI process or “cell”, or for one CSI process or “cell”) is used inaddition to the CSI request field in order to select one out of K_(A)=2values of ‘resourceConfig’ defined in the second step resourceconfiguration. In general, for a given value of K_(A), ┌log₂K_(A)┐ bits(per CSI process or “cell”; or for one CSI process or “cell”) can beadded for selecting one out of K_(A) values. Alternatively, instead ofadding ┌log₂K_(A)┐ bits for selecting one out of K_(A) values, someexisting code points in the UL-related DCI can be reused for thispurpose thereby reducing the number of or removing the need foradditional bits.

In a second example, the number of CSI-RS ports N_(PORT) is included asan RRC parameter (such as ‘antennaPortsCount’) in the RRC configurationIE ‘CSI-RS-Config’ along with other CSI-RS parameters (such as pC). Inaddition, a set of K values of the time-frequency pattern‘resourceConfig’, where K=8, is also included in the RRC configurationIE ‘CSI-RS-Config’. For aperiodic CSI-RS, subframe configuration is notpresent. In the second step, a set of K_(A) values of ‘resourceConfig’,where K_(A)=2, is configured via activation/deactivation mechanism. Thatis, 2 out of 8 possible values of ‘resourceConfig’ are selected for theUE in the second-step CSI-RS resource configuration. For this purpose, a6-bit (3 bits per value) field is needed to signal the selection, eitherin a MAC CE (cf. example in FIG. 7A, where the MAC CE includes‘resourceConfig’) or a DCI used for activation/deactivation. In thethird step, one additional bit (per CSI process or “cell”) is used inaddition to the CSI request field in order to select one out of K_(A)=2values of ‘resourceConfig’ defined in the second step resourceconfiguration. In general, for a given value of K_(A), ┌log₂K_(A)┐ bits(per CSI process or “cell”; or for one CSI process or “cell”) can beadded for selecting one out of K_(A) values. Alternatively, instead ofadding ┌log₂K_(A)┐ bits for selecting one out of K_(A) values, someexisting code points in the UL-related DCI can be reused for thispurpose thereby reducing the number of or removing the need foradditional bits.

In a third example (also applicable to the previous two examples), givena size-K_(A) subset of NZP CSI-RS resources currently activated for theUE (from the previous step), a ┌log₂ (K_(A))┐-bit CSI-RS resourceselection field to select one out of K_(A) activated resources can beintroduced in an UL-related DCI. Alternatively, at least one of the usedor required K_(A) code points for signaling this selection can reusecode point(s) (either reserved code points or borrowed from other unusedfeature(s)) from the existing code point(s) in the DCI. If there areK_(A) available code points, no additional bit needs to be introduced.Otherwise, the number of additional bits for CSI-RS resource selectioncan be reduced.

The fourth component (that is, aperiodic CSI-RS CSI reference resource)regulates the manner in which a UE measures aperiodic CSI-RS. Asdescribed in FIGS. 5 and 6 (640 and 650), a UE performs aperiodic CSIreporting in subframe n=m+L upon decoding in subframe n either an uplinkDCI format, or a Random Access Response Grant containing a CSI requestfield which is set to trigger a CSI report. It is further described thata CSI-RS (in this case, aperiodic CSI-RS) is transmitted within the samesubframe containing the trigger (the CSI request field in either theassociated uplink DCI format or a Random Access Response Grant) for theCSI report. In other words, the aperiodic CSI reporting performed insubframe m is a response of a CSI request field in subframe n−L. Tocalculate this CSI, CSI-RS located within a same subframe no later thanthe associated CSI reference resource (defined by a single downlink orspecial subframe n−n_(CQI) _(_) _(ref)) is used. This CSI referenceresource is located on or after the subframe containing the trigger (theCSI request field in either the associated uplink DCI format or a RandomAccess Response Grant) for the CSI report.

In particular, the following description for aperiodic CSI calculationin relation to CSI reference resource for some scenarios is given asfollows (from REF3 section 7.2.3).

For a UE in transmission mode 9 or 10 and for a CSI process, if the UEis configured with parameter eMIMO-Type by higher layers, and eMIMO-Typeis set to ‘CLASS A’, and one CSI-RS resource configured, or the UE isconfigured with parameter eMIMO-Type by higher layers, and eMIMO-Type isset to ‘CLASS B’, and parameter channelMeasRestriction is not configuredby higher layers, the UE shall derive the channel measurements forcomputing the CQI value reported in uplink subframe n and correspondingto the CSI process, based on only the non-zero power CSI-RS (defined in[3]) within a configured CSI-RS resource associated with the CSIprocess.

For a UE in transmission mode 9 or 10 and for a CSI process, if the UEis configured with parameter eMIMO-Type by higher layers, and eMIMO-Typeis set to ‘CLASS B’, and parameter channelMeasRestriction is configuredby higher layers, the UE shall derive the channel measurements forcomputing the CQI value reported in uplink subframe n and correspondingto the CSI process, based on only the most recent, no later than the CSIreference resource, non-zero power CSI-RS (defined in [3]) within aconfigured CSI-RS resource associated with the CSI process.

The CSI reference resource for a serving cell is defined as follows:

-   -   For a non-BL/CE UE, in the frequency domain, the CSI reference        resource is defined by the group of downlink physical resource        blocks corresponding to the band to which the derived CQI value        relates. For a BL/CE UE, in the frequency domain, the CSI        reference resource includes all downlink physical resource        blocks for any of the narrowband to which the derived CQI value        relates.    -   In the time domain and for a non-BL/CE UE,        -   for a UE configured in transmission mode 1-9 or transmission            mode 10 with a single configured CSI process for the serving            cell, the CSI reference resource is defined by a single            downlink or special subframe n-n_(CQI) _(_) _(ref),            -   where for aperiodic CSI reporting, if the UE is not                configured with the higher layer parameter                csi-SubframePatternConfig-r12,            -   n_(CQI) _(_) _(ref) is such that the reference resource                is in the same valid downlink or valid special subframe                as the corresponding CSI request in an uplink DCI                format.            -   n_(CQI) _(_) _(ref) is equal to 4 and subframe n−n_(CQI)                _(_) _(ref) corresponds to a valid downlink or valid                special subframe, where subframe n−n_(CQI) _(_) _(ref)                is received after the subframe with the corresponding                CSI request in a Random Access Response Grant.        -   where for aperiodic CSI reporting, and the UE configured            with the higher layer parameter            csi-SubframePatternConfig-r12,            -   for the UE configured in transmission mode 1-9,                -   n_(CQI) _(_) _(ref) is the smallest value greater                    than or equal to 4 and subframe n−n_(CQI) _(_)                    _(ref) corresponds to a valid downlink or valid                    special subframe, where subframe n−n_(CQI) _(_)                    _(ref) is received on or after the subframe with the                    corresponding CSI request in an uplink DCI format;                -   n_(CQI) _(_) _(ref) is the smallest value greater                    than or equal to 4, and subframe n−n_(CQI) _(_)                    _(ref) corresponds to a valid downlink or valid                    special subframe, where subframe n−n_(CQI) _(_)                    _(ref) is received after the subframe with the                    corresponding CSI request in an Random Access                    Response Grant;                -   if there is no valid value for n_(CQI) _(_) _(ref)                    based on the above conditions, then n_(CQI) _(_)                    _(ref) is the smallest value such that the reference                    resource is in a valid downlink or valid special                    subframe n−n_(CQI) _(_) _(ref) prior to the subframe                    with the corresponding CSI request, where subframe                    n−n_(CQI) _(_) _(ref) is the lowest indexed valid                    downlink or valid special subframe within a radio                    frame;            -   for the UE configured in transmission mode 10,                -   n−n_(CQI) _(_) _(ref) is the smallest value greater                    than or equal to 4, such that the value corresponds                    to a valid downlink or valid special subframe, and                    the corresponding CSI request is in an uplink DCI                    format;                -   n_(CQI) _(_) _(ref) is the smallest value greater                    than or equal to 4, and subframe n−n_(CQI) _(_)                    _(ref) corresponds to a valid downlink or valid                    special subframe, where subframe n−n_(CQI) _(_)                    _(ref) is received after the subframe with the                    corresponding CSI request in a Random Access                    Response Grant;

In the present disclosure, several embodiments for aperiodic CSI-RSlocation and CSI reference resource subframe are given below.

In one embodiment, when a UE is configured with aperiodic CSI-RS (forexample, via any of the configuration embodiments discussed above), thenon-zero-power CSI-RS used to calculate CSI is located in the subframecontaining the trigger (the CSI request field in either the associateduplink DCI format or a Random Access Response Grant) for the CSI report.In addition, the CSI reference resource n−n_(CQI) _(_) _(ref) is definedby a same valid downlink or valid special subframe as the correspondingCSI request in an uplink DCI format. In this embodiment, n−n_(CQI) _(_)_(ref) is chosen to be the same as that for the legacy periodic CSI-RS.For a UE configured in transmission mode 1-9 or transmission mode 10with a single configured CSI process for the serving cell, threepossibilities exist. First, n_(CQI) _(_) _(ref) is equal to 4. Second,n_(CQI) _(_) _(ref) is the smallest value greater than or equal to 4,such that the value corresponds to a valid downlink or valid specialsubframe, and the corresponding CSI request is in an uplink DCI format.Third, n_(CQI) _(_) _(ref) is the smallest value greater than or equalto n−n_(CQI) _(_) _(ref) corresponds to a valid downlink or validspecial subframe, where subframe n−n_(CQI) _(_) _(ref) is received afterthe subframe with the corresponding CSI request in a Random AccessResponse Grant.

In another embodiment, when a UE is configured with aperiodic CSI-RS(for example, via any of the configuration embodiments discussed above),the non-zero-power CSI-RS used to calculate CSI is located in thesubframe containing the trigger (the CSI request field in either theassociated uplink DCI format or a Random Access Response Grant) for theCSI report. In addition, the CSI reference resource n−n_(CQI) _(_)_(ref) is defined by a same valid downlink or valid special subframe asthe corresponding CSI request in an uplink DCI format. In thisembodiment, n_(CQI) _(_) _(ref) is chosen to be different from that forthe legacy periodic CSI-RS. An additional X-subframe time is added tothe UE processing time when a UE is configured with aperiodic CSI-RS.For instance X=1 can be chosen. In this case, for a UE configured intransmission mode 1-9 or transmission mode 10 (for LTE) with a singleconfigured CSI process for the serving cell, three possibilities exist.First, n_(CQI) _(_) _(ref) is equal to 5. Second, n_(CQI) _(_) _(ref) isthe smallest value greater than or equal to 5, such that the valuecorresponds to a valid downlink or valid special subframe, and thecorresponding CSI request is in an uplink DCI format. Third, n_(CQI)_(_) _(ref) is the smallest value greater than or equal to 5, andsubframe n−n_(CQI) _(_) _(ref) corresponds to a valid downlink or validspecial subframe, where subframe n−n_(CQI) _(_) _(ref) is received afterthe subframe with the corresponding CSI request in a Random AccessResponse Grant.

In a variation of this embodiment, the value of X (a subframe offset forn_(CQI) _(_) _(ref) from 4) is not fixed and can be configured viahigher-layer (RRC) signaling for a given UE. For example, an RRCparameter SubframeOffsetApCSIRS can be used to configure the value of Xfrom {0, 1, or 2}. Alternatively, the value of X can be made a UEcapability.

FIG. 10 illustrates a flowchart for an example method 1000 wherein a UEreceives CSI-RS resource configuration information according to anembodiment of the present disclosure. For example, the method 1000 canbe performed by the UE 116.

The method 1000 begins with the UE receiving CSI-RS resourceconfiguration information which includes K≥1 CSI-RS resources (step1001). This configuration information can be sent to the UE viahigher-layer (such as RRC) signaling. Since this CSI-RS resourceconfiguration corresponds to aperiodic CSI-RS, subframe configuration(which includes periodicity and subframe offset) can be absent from thisconfiguration. In addition, this configuration information cancorrespond to CLASS B eMIMO-Type. In a subframe, the UE receives anUL-related DCI containing an aperiodic CSI (A-CSI) request (step 1002)along with a CSI-RS associated with a selected CSI-RS resource. Inreference to the CSI-RS, the UE calculates A-CSI (step 1003) andtransmits the A-CSI on an UL channel (step 1004).

The selected CSI-RS resource is taken from the K CSI-RS resourcesassigned to the UE. When K=1, the selected CSI-RS resource is the sameas the resource included in the CSI-RS resource configurationinformation. When K>1, the selection of one CSI-RS resource can be donein one or two steps. In the one-step selection, the UL-related DCIincludes an indication of which one of the K CSI-RS resources isselected. On the two-step selection, N (<K) CSI-RS resources are firstselected by activating N out of K configured resources. This is thenfollowed by an indication (in the UL-related DCI) of which one of the NCSI-RS resources is selected. The activation of N out of K configuredresources can be signaled via either MAC CE or L1 downlink controlsignaling.

FIG. 11 illustrates a flowchart for an example method wherein a BSconfigures a UE (labeled as UE-k) with CSI-RS resource. For example, themethod 1100 can be performed by the eNB 102.

The method 1100 begins with the BS configuring UE-k with K≥1 CSI-RSresources (step 1101). This information is included in CSI-RS resourceconfiguration information. This configuration information can be sent tothe UE via higher-layer (such as RRC) signaling. Since this CSI-RSresource configuration corresponds to aperiodic CSI-RS, subframeconfiguration (which includes periodicity and subframe offset) can beabsent from this configuration. In addition, this configurationinformation can correspond to CLASS B eMIMO-Type. In a subframe, the BStransmits an UL-related DCI containing aperiodic CSI (A-CSI) request toUE-k along with a CSI-RS which is associated with a selected CSI-RSresource (step 1102). After a few subframes, the BS receives therequested A-CSI reporting on an UL channel from UE-k (step 1103).

The selected CSI-RS resource is taken from the K CSI-RS resourcesassigned to UE-k. When K=1, the selected CSI-RS resource is the same asthe resource included in the CSI-RS resource configuration information.When K>1, the selection of one CSI-RS resource can be done in one or twosteps. In the one-step selection, the UL-related DCI includes anindication of which one of the K CSI-RS resources is selected. On thetwo-step selection, N (<K) CSI-RS resources are first selected byactivating N out of K configured resources. This is then followed by anindication (in the UL-related DCI) of which one of the N CSI-RSresources is selected. The activation of N out of K configured resourcescan be signaled via either MAC CE or L1 downlink control signaling.

Although FIGS. 10 and 11 illustrate examples of methods for receivingconfiguration information and configuring a UE, respectively, variouschanges could be made to FIGS. 10 and 11. For example, while shown as aseries of steps, various steps in each figure could overlap, occur inparallel, occur in a different order, occur multiple times, or not beperformed in one or more embodiments.

Although the present disclosure has been described with exampleembodiments, various changes and modifications can be suggested by or toone skilled in the art. It is intended that the present disclosureencompass such changes and modifications as fall within the scope of theappended claims.

What is claimed:
 1. A user equipment (UE) comprising: a transceiverconfigured to receive information indicating a channel state informationreference signal (CSI-RS) resource configuration, an activation messagefor a CSI-RS, and the CSI-RS that is associated with a selected CSI-RSresource; and a processor operably connected to the transceiver, theprocessor configured to calculate CSI in reference to the CSI-RS,wherein the transceiver is further configured to report the CSI bytransmitting the CSI on an uplink channel, wherein the activationmessage indicates a starting transmission time interval of the CSI-RS,wherein the information indicating the CSI-RS resource configuration isreceived via higher-layer signaling, and wherein the CSI-RS resourceconfiguration includes a periodicity and an offset.
 2. The UE of claim1, wherein the activation message is received via a medium accesscontrol (MAC) control element (CE).
 3. The UE of claim 2, wherein adeactivation message indicating an ending transmission time interval ofthe CSI-RS is received via the MAC CE.
 4. The UE of claim 1, wherein theactivation message is included in downlink control information (DCI) andreceived via a physical downlink control channel (PDCCH).
 5. The UE ofclaim 4, wherein a deactivation message indicating an endingtransmission time interval of the CSI-RS is included in the DCI andreceived via the PDCCH.
 6. A base station (BS) comprising: a processorconfigured to generate information indicating a channel stateinformation reference signal (CSI-RS) resource configuration and anactivation message for a CSI-RS; and a transceiver operably connected tothe processor, the transceiver configured to: transmit the informationindicating the CSI-RS resource configuration, the activation message forthe CSI-RS, and the CSI-RS that is associated with a selected CSI-RSresource, and receive CSI calculated in reference to the CSI-RS reportedon an uplink channel, wherein the activation message indicates astarting transmission time interval of the CSI-RS, wherein theinformation indicating the CSI-RS resource configuration is transmittedvia higher-layer signaling, and wherein the CSI-RS resourceconfiguration includes a periodicity and an offset.
 7. The BS of claim6, wherein the activation message is transmitted via a medium accesscontrol (MAC) control element (CE).
 8. The BS of claim 7, wherein adeactivation message indicating an ending transmission time interval ofthe CSI-RS is transmitted via the MAC CE.
 9. The BS of claim 6, whereinthe activation message is included in downlink control information (DCI)and transmitted via a physical downlink control channel (PDCCH).
 10. TheBS of claim 9, wherein a deactivation message indicating an endingtransmission time interval of the CSI-RS is included in the DCI andtransmitted via the PDCCH.
 11. A method for operating a user equipment(UE), the method comprising: receiving information indicating a channelstate information reference signal (CSI-RS) resource configuration, anactivation message for a CSI-RS, and the CSI-RS that is associated witha selected CSI-RS resource; calculating CSI in reference to the CSI-RS;and reporting the CSI by transmitting the CSI on an uplink channel,wherein the activation message indicates a starting transmission timeinterval of the CSI-RS, wherein the information indicating the CSI-RSresource configuration is received via higher-layer signaling, andwherein the CSI-RS resource configuration includes a periodicity and anoffset.
 12. The method of claim 11, wherein the activation message isreceived via a medium access control (MAC) control element (CE).
 13. Themethod of claim 12, wherein a deactivation message indicating an endingtransmission time interval of the CSI-RS is received via the MAC CE. 14.The method of claim 11, wherein the activation message is included indownlink control information (DCI) and received via a physical downlinkcontrol channel (PDCCH).
 15. The method of claim 14, wherein adeactivation message indicating an ending transmission time interval ofthe CSI-RS is included in the DCI and received via the PDCCH.